The object of the game is to put the opponent's king in check so securely that escape is impossible. This is called checkmate. When checkmate is accomplished while another opponent remains in the game, the checkmated king is removed from the chess board and the checkmated player's pieces are conscipted into the service of the player that accomplished the checkmate. (See below.) The full credit for the checkmate goes to the checkmating player and is not shared.

Red checkmates White with a knight and a rook.
The red knight moves into White's tridrant, checkmating White. It's White's turn but White has no piece that can capture the red knight, and knights cannot be blocked. Escape is impossible. The three hexes within the white king's reach are under threat by the checking knight and the red rook in White's tridrant. Red has checkmated White. The white king will be removed from the chess board. The remaining white pieces are left on the board and are now under Red's command.

Checkmate Pending

When a player checkmates the opponent to their right, the opponent to their left gets the next turn and might be able to interfere. This condition is called checkmate pending.

Red tentatively checkmates Black with the queen and knight
The red queen tentatively checkmates the black king. It's White's turn. The white knight is preventing the black king from escaping (to b1). Since checkmates are not shared, White will likely move the knight to prevent Red from checkmating Black.