We can't see your last move here, so I'm going to assume you played R3a3
Assuming my low-elo brain is correct (I'm not currently using analysis), this should fall under the categories of a brilliant.
If black takes the bishop, Ra5 would allow Qxb5+, which would win two pawns and eventually the deadly g-file rook when the king is forced to the eighth rank.
If black does not take the rook, however, it leads to the same problem. White should still play Ra5, followed by Qxb5+, and once again black is a bit screwed.
Please do not trust me fully on this. I did not use analysis and I am definitely not a great chess player by any means.
Is this a brilliant move at the end, the rook sacrifice? This was the ending of a game I played and he abandoned it.