In its more widely-known usage, challah refers to the two loaves of bread that form the core of the Shabbat meal. But in its more basic, biblical meaning, challah is the piece of dough that is separated and consecrated to G-d every time we bake bread
You thought challah refers to the two braided loaves of bread reserved for Shabbat meals? It does, but mainly, challah is the small chunk of dough we tear off and burn . . .