so what we can notice here is that the knight is protected by the queen , so if queen takes on g7 , black can go rook g8 ( the f knight protects the rook when it moves on g8) or he can go Rook f8.
so queen takes on g7 only wins a pawn , what's better is to look at undefended pieces , black's dark square bishop is undefended ( Remember tactics arise from opponent's undefended pieces or lack of harmony between the pieces or an expposed king).
so based on that , when the queen takes on e5 with check , black would either move to f8 or play bishop e6 or qe7 , at all those cases , we can simply take the free bishop on a5 .
hopefully it's clear now.
Chess Tactics and Training Puzzles - Chess.com
i found a queen fork between the knight and the rook and i got it wrong HELP