You and your opponent are each in charge of an army. Your goal: to catch the other army's king (before they catch yours)! When you have him attacked and he can no longer escape, it's called "checkmate," and you win! You each start with a trusty army of 16: the King, Queen, two Rooks, two Bishops, two Knights, and eight Pawns.
At the beginning of the game the chessboard is laid out so that each player has the white (or light) color square in the bottom right-hand side. The chess pieces are then arranged the same way each time. The second row (or rank) is filled with pawns. The rooks go in the corners, then the knights next to them, followed by the bishops, and finally the queen, who always goes on her own matching color (white queen on white, black queen on black), and the king on the remaining square.
The player with the white pieces always moves first, so it's only fair to take turns playing white and black. On each turn you get to move one of your pieces (except for one special move). Then it's your opponent's turn. And back and forth, you take turns until one of the kings is cornered... or your whole army is tired out!
Each of the 6 different kinds of pieces has its own shape for moving. Most pieces cannot move through other pieces-- only the knight can jump over anyone who gets in his way! Also no piece can ever move onto a square with one of their own pieces. However, they can be moved to take the place of an opponent's piece: that's how you capture the enemies!