Fold equity
The extra value a bet or raise carries from the chance it wins the pot outright by making the opponent fold, on top of whatever raw equity the hand has if called.
A shove that only wins at showdown has none of it: calling has no fold equity, since the caller can only win by having the better hand. A shove that also wins outright a good share of the time when the opponent folds carries real fold equity on top of its showdown chances, which is exactly why the shover in a push/fold spot can profitably jam hands that would lose most showdowns.