Chess is an amazing game that is fairly easy to learn and hard to master. 

THE BASICS 

There are 6 pieces in chess the king, the queen, the bishop, the Knight, the rook, and the pawn. A chess board is 8x8 squares that alternates between white and black squares. White and black play each other. There is one king and one king,  two bishops, two knights, two rooks, and 8 pawns per color. The king and queen are in the middle back squares the rooks in the corners, the knights next to the rooks, the bishops left and right of the king and queen, and the pawns in front of all the pieces. Horizontal rows are called ranks the vertical rows are called files. 

THE PAWNS 

The pawn can move forward one space and attacks other pieces diagonally forward, the first time you move a pawn it can move 2 spaces. The pawn's greatest weakness is that it is the only piece that can't move backwards. Pawns are a minor piece and are worth one piece. If a pawn reaches the end of the board it can promote into any piece except for a pawn or king. Pawns are also important for structure. (see TACTICS, PAWN STRUCTURE). 

En Passant 

En Passant is a special pawn move and means "in passing" in French. It's a rare move that can be a little confusing. It occurs on the 5th and 4th ranks and it's where a pawn moves up two squares and an adjacent opposing pawn takes it as if it moved only one square. There is also a rare en passant checkmate. The regular en passant is shown in the first image below, the checkmate is the second: The white pawn moves up capturing the pawn on f5 opening an attack from the bishop this is a check mate against Magnus Carlsen  

The KNIGHT

The Knight is an interesting piece, it moves in an "L" shape in any direction it can also jump over pieces. The Knight often resembles a horse. Knights are famous for delivering forks (see TACTICS, FORKS). Pro tip: a Knight on the rim is grim which means Knights are more powerful when in the middle of the board then when on the edge a Knight in the middle of the board is sometimes called the "Octopus Knight" because it has 8 possible moves. 

The Bishop

The Bishop is a tall piece with a pointed head and a diagonal slit in the side of it. They move diagonally and stay on the same color the whole game, they can fly across the board in one move. You start with 2 bishops one on each color when a player has both of their bishops it is called a bishop pair. Bishops and Knights are called minor pieces, and go together. Knights can touch every square but are slow bishops that move very fast but can only be on half the squares (32). 

The Rook 

Rooks start in the corners of the board they move horizontally and vertically across the board rooks can reach any square on the board and they are fast. Rooks look a lot like a castle. Rooks are a very valuable and powerful piece. 

The Queen 

The Queen is the piece you get if you merge a rook and a bishop, it moves horizontally, vertically, and diagonally. Note that bishops do not have Knight powers and can't move in an "L" shape or jump over pieces. 

The King

The King moves only one square in any direction as long as it is not a square being attacked by an opponent's piece. The King is very vulnerable, it is also the most valuable piece and is worth the entire game. This website is also named after the King. 

Castling

Castling is a special move where you move the king two squares and the rook jumps over it. This move protects the king and develops the rook allowing it to get some action. 

Material

Each piece is worth a certain amount of points that help you keep track of how powerful your army is, but points don't actually have any value it's just a system to determine if a trade is good or bad (A trade is where you take a piece and your opponent takes takes back). The piece values are listed below. 

Pawn=1 

Knight=3

Bishop=3

Rook=5

Queen=9

King- cannot be traded 

pro tip: Chess Masters consider the bishop to be worth 3.25 in comparison to the Knight because of it's range. 

You always want to make a trade that is better for you for example two bishops for a rook since 6 (or 6.5) is greater than 5. 

Material isn't the only advantage so don't get ahead of yourself and think your winning just because you have more material. (See STRATEGY, TYPES OF ADVANTAGES.) 

Check

Check occurs when a piece is attacking the king and the king HAS TO stop it. There are three ways to stop check: Run away and move to a square that is not under attack, block the attack using one of your pieces, or capture the attacking piece.

Checkmate 

Your goal is to checkmate your opponent. Checkmate is when a king is in check and cannot block the attack, capture the attacking piece, or move to a safe square that is not being attacked. There are names for certain checkmates such as the fools-mate, bulldozer checkmate, and the ladder checkmate. The fastest checkmate is the two-move checkmate as shown below.

Draws

When a game of chess ends in a tie it is called a draw. In chess tournaments if you lose you get zero points if you win you get one point and if you draw you and your opponent gets half a point. 

The player who is winning avoids the draw while the play that is losing typically is happy to draw. 

The types of draws are... 

Insufficient mating material 

Stalemate

Repetition

50 move draw

draw by agreement 

There are also clock draws (see CLOCKS, BASICS)  

Insufficient Mating Material 

A draw by insufficient mating material is when neither player has enough material to checkmate. It is an endgame position where there simply are not enough pieces left. Some examples are king, king and bishop, king or king and knight. King and pawn is not a draw because the pawn can advance and promote into a queen or rook (see ENDGAME, STRATEGY) There is a variant of this draw called a dead position which is where there is technically still a checkmate but the losing player would have to do very specific moves, examples of this draw would be two knights or a Knight and a bishop. 

Stalemate 

The rules of chess say that you have to move when it's your turn so what happens if there are no legal moves, that is stalemate and it ends in a draw. Stalemates are common in beginner games because beginners tend to not plan ahead or toy with their opponents by getting three or more queens. In master games stalemates almost never happen because Masters always plan several moves ahead. The position shown below is stalemate because the bishop blocks the square next to the king and the queen blocks the two other squares. 

Draw by repetition

A draw by repetition or threefold repetition is when (black and white pieces) are in the same position three times. This is a rule because a player, typically the one who is losing checks the opposing king over and over the same way this is known as the perpetual check the first image below demonstrates this. The Bishop goes back and forth while the Knight protects both squares. There is also a fivefold draw Which is unlike the threefold draw is enforced and a mandatory draw. The threefold draw is an optional draw and must be claimed by a player. 

50-move draw

This draw is the least common and can only be claimed when the game has gone for 50 moves without a pawn being moved or a piece being captured, it was designed to prevent games from going on for forever. A pawn being moved is progress towards promotion and a piece being captured means something is actually happening, a way to annoy your opponent is to have a pawn on the backrank and when it's move 49 move the pawn. A type of 50-move draw is the 75-move draw which like the fivefold repetition draw is mandatory. 

Draw By Agreement (offering a draw) 

At any point in the game a player can offer a draw. The draw offer stands for one move and can be accepted or declined immediately or the player can think about it. It is proper to offer a draw on your move and to not offer a draw repeatedly in a lost position. If a draw is offered you should think about why your opponent wants a draw. A draw may be offered by a winning player if a draw would win a tournament and there is no need for a win. 

Touch Move Rule

Touch move means that if you touch a piece and you can legally move that piece you have to move it. Touch take means that if you touch an opponent's piece with your piece you have to take it if it is legal. New players tend to like to touch the pieces and an easy way to fix this is to practice it in regular games so you don't have a problem in a tournament where these rules are strictly enforced. 

Tactics

Tactics are how you move the pieces. It is pretty advanced and capturing your opponent's pieces and saving your own pieces. 

Free stuff

Free stuff or hanging pieces are pieces that are undefended and that you can capture easily they are most commonly pawns but can also be more important. A pawn may not look like much but can actually be worth a lot in the end game especially when it comes to masters. 

Pins

A pin is the most common tactical move. It is where you line up your piece with one of your opponent's less valuable pieces with a more valuable pieces behind it. For example a bishop attacking a pawn with the king behind it. The advantage of this is that the pawn can't move forward. There are two types of pins: an absolute pin where the piece can not move or it is illegal this involves the king. There is also a relevant where it would be bad to move your piece because you lose a valuable piece most commonly a queen. The way to counter a pin is to move the piece behind the pinned piece this is called breaking the pin. The first image below is a relevant pin the second and third are obsolete. 

Skewers

A skewer is the opposite of a pin, instead of the least valuable piece that can't move in front of the more valuable piece the more valuable piece is in front of the less valuable piece and should or must move and the piece attacking it can then take the piece behind it. The most powerful kind of skewer is a royal skewer where the king is checked and must move reviling the king behind it. 

Forks

A double attack is where you attack two pieces at once and they are one of the more common tactical moves. The most common type of double attack is a fork. Any piece can fork but it is most commonly a pawn or a Knight. Forks are useful because (especially if the piece that is forking is less valuable than the pieces being forked) the attacker will gain material almost every time. If you fork a king and a queen the king is checked and has to move therefore giving the attacker a queen, this is called a royal fork. Knights are famous for forking and are the most common piece used to fork. There is a way to defend a fork, if you check your opponent's king with one of the pieces that is being forked you can escape the fork because the opponent is forced to defend the check giving the forked player a chance to save the other piece, this is harder if more than one piece is being forked. When forking your opponent make sure that the piece that is forking cannot be taken. 

Discoveries

A discovered attack is a type of double attack and is where a piece that is blocking another piece moves attacking a piece and reveling the piece behind it that also is attacking a piece. There are four main types of discoveries with pictures below they are, (in this order) Discovered check, discovered attack, double check, and double attack. The discovered check is just what it sounds like: a piece moves reviling a piece behind it that checks the king, a discovered attack is where a piece moves and the piece behind it attacks a piece and double check and double attack are just the same as the first two but the piece moving away either attacks a piece of checks the king. The advantage of double check is that the king has to move because if you block one piece the other is still attacking. There is no such thing as triple check because that would mean the king was already in check. 

Sacrifices

A sacrifice or sac in chess is exactly what it sounds like: giving up a piece that you usually wouldn't give up in order to gain material later on, an advantage, or checkmate. This will make more sense if you look at positions of sacrifices, but keep in mind that most sacrifices fail and it is a very risky tactic. I will let you try to figure out what this sacrifice does.