attacking piece no relation skewer
A pin is one of the most powerful tactics in chess in which a defending piece cannot move out of an attacking piece's line of attack without exposing a more valuable defending piece. Moving the attacking piece to effect the pin is called pinning; the defending piece restricted by the pin is described as pinned. Only a piece that can move any number of squares along a horizontal, vertical, or diagonal line (i.e. a bishop, rook, or queen) can pin. Any piece can be pinned except the king. 
The inverse of a pin is a skewer, in which a more valuable piece under direct attack may move to expose a less valuable piece to an attack.
no relation