Stalemate is a situation where the player whose turn it is to move is not in check but has no legal move. When stalemate occurs, the game ends as a draw.
In the diagram on the left, white is stalemated and cannot move his king. Even though he is losing in pieces, the game is a draw!
If you are winning, make sure to avoid an accidental stalemate!
If you are losing, you can look for opportunities to be stalemated.
In rare cases, you can force a stalemate. In the diagram on the left, even if black did not move the bishop there, as long as white plays correctly, he can force an eventual draw due to the way the black pawn is positioned on the side, and the black bishop is a dark square bishop (opposite color of the square the white king is in)