Examples

White can sacrifice the exchange with Rxf5!
Recapturing lures the king to f5, where it can be attacked with the skewer Bh3+!

Sometimes the rear piece can be decoyed into a skewer:

White can sacrifice a rook with Rb8+!
Black has to capture the rook with Qxb8, and the queen is lured to b8.
White can now win with the skewer Rh8+.

Related combinations

Trade into skewer is similar to decoy into skewer, but the first move is a trade instead of a sacrifice. It is also possible to decoy a piece to a square where it can be attacked in a subsequent tactic other than a skewer. And you can decoy the king into checkmate.