Pin
Also called Absolute pin, Relative pin.
A piece cannot move without exposing a more valuable piece behind it.
Bishop to b5 pins the knight on c6 to the king on e8: the knight may not move, because that would expose the king. Black played …d6, which opened the diagonal.
A pin to the king is absolute: the pinned piece cannot legally move. A pin to anything else is relative: it can move, but it costs. Pile up on a pinned piece, because it cannot run.
New to chess? The examples here use it. Play your first moves (five minutes), then learn chess from the beginning, one short lesson at a time.
Practise it here: ten puzzles on this idea, at a level you choose, counted in your progress.
Want more? Puzzles on this from real games, on Lichess, free and with no account. They are not counted in your progress here.
Learn and practise it
- Lesson: The pin