Relative pins are the type of pin when a piece is pinned to another piece. Relative pins, though, unlike absolute pins where the piece is pinned to a king, can be broken, by moving the pinned piece away since it is legal. In fact there are many unpinning combinations designed to counter faulty relative pins like when players prematurely play Bg4 to pin the queen's knight to the queen.
But not all relative pins are like that, some can be very effective and result in immobilising of the pieces. After it is immobilised, you can attack it with more force and win it. Here is an example of that in action:
Pins are effective weapons and can be useful. Hope you liked it!