I need help to know what happened here
literally this player makes an impossible move
It's called en passant. A pawn can take a pawn that moves two squares as if it had only moved one (on the next move only). A basic rule of chess.

I need help to know what happened here
you hung a pawn and forgot that white can capture it with en passant, the french move.
and honestly, you WANT them to take the pawn so you can mae in 1 with qf5#
and this