The goal
Checkmate the king
Attack the other king so that it cannot escape. You never capture the king: the game ends the move before.
How the pieces move
King
One square in any direction.
Queen
Any distance along a rank, a file or a diagonal.
Rook
Any distance along a rank or a file.
Bishop
Any distance along a diagonal. It stays on one colour.
Knight
Two squares one way and one across. It is the only piece that jumps.
Pawn
One square forward, or two from its first square. It captures one square diagonally.
Special moves
Castling
The king moves two squares towards a rook and the rook jumps over it. Neither may have moved, the squares between must be empty, and the king may not be in check, pass through an attacked square or land on one.
En passant
When a pawn moves two squares and lands beside your pawn, you may capture it as if it had moved one. Only on the very next move.
Promotion
A pawn that reaches the far rank becomes a queen, a rook, a bishop or a knight. You choose.
Check
Check
Your king is attacked. You must move it, block the attack or capture the attacker.
Checkmate
Your king is attacked and nothing saves it. The game is over.
Draws
Stalemate
The player to move is not in check and has no legal move.
Fifty-move rule
Fifty moves by each side with no capture and no pawn move.
Threefold repetition
The same position, with the same player to move, comes up three times.
Not enough pieces
King against king, or king against king and a single bishop or knight.
Out of time
With a clock on, a player whose time runs out loses. If the other side has only a king left, it is a draw.