Even though there are 64 squares and only 32 pieces, those squares can run out and your pieces can be left out without legal moves and getting trapped. It is a frustrating situation when you can't save a piece from being taken because you didn't foresee it would get trapped a few moves before.
Sometimes, even with a pawn move, you can take away your opponent's safe squares. Even queens are vulnerable to be trapped because any trade for a lesser piece is dangerous.
The Queen is such a powerful piece and it controls so many squares, it is hard to believe it can be trapped, but with the correct tactics and a positive position, every piece is trappable.
This knight wants to take what looks like a free pawn, but it would break the implicit law of not getting your knight on the edge of the board.
But that gives black the chance to trap the knight, can you see it?
That's right, Bishop to A4 traps the knight forever and the king can just come and take it with no issue in the next couple of turns.