The object is to remove your opponent's pieces or prevent them from moving. Pieces move forward and diagonally, and can jump and remove opposing pieces by landing in the empty space directly behind them. When a piece reaches the last row, it is promoted to a king (represented by two stacked game pieces). Kings can move backwards and well as forwards. Whenever you can make a jump, you must do so. See The object is to remove your opponent's pieces or prevent them from moving. Pieces move forward and diagonally, and can jump and remove opposing pieces by landing in the empty space directly behind them. When a piece reaches the last row, it is promoted to a king (represented by two stacked game pieces). Kings can move backwards and well as forwards. Whenever you can make a jump, you must do so. The Wikipedia entry has more detailed rules.
Player 1 (red) can make a double jump to the highlighted cells, removing the two jumped blue pieces.