White sacrificed a piece to attack the Black King but Black was able to defend.
After 1. Qxg4 White can still hold the game.
But White moved 1. Re1? there follows 1. ...Qxe1? 2. Qxe1 Rd1 3. Qxd1 Nf2+ wins.
However there is a forced mate after 1. Re1 that I missed. Find the key move to force mate 😀