What "relative pin" means in chess

A relative pin is a situation where a piece is unable to move because its movement would expose a more valuable piece behind it to capture. This is called a relative pin because the pinned piece is not actually immobilized, but rather it is in a position where it is disadvantageous to move. The piece that is being attacked is called the pinned piece, while the piece that would be threatened if the pinned piece moved is called the protected piece. Relative pins can be a useful tool for players looking to gain an advantage over their opponent by limiting their movement options.