A fold is a _ in a rock, and a fault is a _in a rock?

A geological fold occurs when one or a stack of originally flat and planar surfaces, such as sedimentary strata, are bent or curved as a result of permanent deformation.

So A fold is a Bend? in a rock. Maybe.

A fault is a planar fracture or discontinuity in a volume of rock, across which there has been significant displacement as a result of rock - mass movement.