Capturing the Enemy
Enemies are usually captured by surrounding them on two opposite sides with your own pieces; this is called custodianship. The piece trapped between the aggressors is removed from the board. It is usually acceptable to place a piece deliberately between two enemies without harm; capture must be a deliberate act.
There is often a special rule of capture for the king, called enclosure, where he must be surrounded on all four sides to capture him. In some games this applies only when the king is on his central square, in others it may affect him anywhere on the board, making the king a very powerful piece.
In most games, the king can help to make captures like any other piece. There are some in which he can't, however. These are usually games in which he would otherwise be too strong: games where he wins on reaching an edge, and requires four attackers to capture him.
Special rules cater for situations where a piece would be otherwise invincible; a king sitting next to his central square can be captured by surrounding him on the other three sides, and a piece next to a restricted corner square may be captured as if that corner square had one of your own men sat upon it.
Next: Gaining the Victory