chess online

1. Rf1 Nd2+
2. Rxd2 Qc3
3. Kc1 Qa1#

The pawn on h3 is sort of a key to this position. It opens up possible mate threats if the queen can get to the a1-h8-diagonal. The white king does have one flight square: d2.
2.Rxd2 blocks this flight square and so the white king can't escape.

In german we call such a tactical motif Hinlenkungsopfer. I'm not completely sure, but I think in english it could be called an attraction sacrifice.