It looks like qd4 would get you a rook back so essentially you got a free pawn and by sacrificing your rook to do so you earned a brilliancy
Brilliant Move

Like @hedafuss wrote after Qxa5 white plays Qe4 forking the king and the rook. So in the end you win a pawn.

Yea brilliancies are awarded for sacrifices. It counts as a sacrifice if you get a better position out of it or if you can recapture after an intermediate move
Can someone explain why this is considered a brilliant move? I only captured a free pawn. In the review, it said: Ignoring the threat on the rook. This is the way to win a pawn. Please. I would appreciate it.