Summary: Shaping is how you build a behavior that isn't in the learner's repertoire yet, by reinforcing closer and closer approximations until you reach the real thing. Task analysis is how you take a big, multi-step skill and chop it into pieces small enough to teach one at a time. You'll lean on both constantly as an RBT, and the exam loves to make sure you can tell them apart.
These two procedures get confused a lot, so let's separate them up front. Shaping changes the form of a single behavior over time. Task analysis breaks a sequence of behaviors into steps. One is about quality, the other is about order. If you keep that distinction in your head, half the exam questions on this topic answer themselves.
Shaping
Shaping is reinforcing successive approximations toward a target behavior until the learner is doing the full target. The key word is approximations. You're not waiting for the finished behavior to show up so you can reinforce it. If you waited, you'd wait forever, because the behavior isn't in the repertoire yet. Instead you reinforce something close, then something a little closer, then closer still.
What "successive approximations" actually means
A successive approximation is a behavior that resembles the target a little more than the last one did. The resemblance is usually in topography (what the behavior looks like), but it can also be in things like loudness, duration, or accuracy.
That's the free preview of Shaping and Task Analysis. The complete guide, plus all 851 practice questions and 3 full exams, is in the study pack and the book.