Sacrifice
A sacrifice is giving up material on purpose to gain an attack, a tactic, or a better position.
The offer is sound when the follow-up wins the material back with interest, or when the king cannot survive. It is a blunder when there is no follow-up.
Bxh7+ is the Greek gift: the bishop takes the h-pawn with check. If the king accepts, a knight and queen can join on the kingside. The bishop is not hanging in the usual sense — it was spent to open the king.
Not every capture on h7 is this idea. You still need a way to bring a knight to g5 and a queen to h5 or the long diagonal. The diagram is the pattern, not a promise that every such position wins.