Summary: Teaching a skill is only half the job. Generalization means the skill shows up with new people, places, and materials you never trained. Maintenance means it sticks around after you stop teaching. If you don't plan for both from day one, you'll end up with a client who can do something perfectly at the table and nowhere else.
Here's the thing nobody tells you when you start. You can run a flawless DTT program, hit mastery in two weeks, and still have done nothing useful. A skill that only happens in your therapy room with your materials and your prompts isn't really a skill the client has. It's a trick they do for you.
The whole point of ABA is socially significant behavior change in the real world. That means the skill has to travel (generalization) and it has to last (maintenance). Don't think of these as something you tack on at the end. You build them in from the first session, or you fight an uphill battle later.
What generalization actually means
Generalization is when a behavior you taught under one set of conditions shows up under conditions you didn't train. There are two flavors, and the exam loves to make you tell them apart.
Stimulus generalization
That's the free preview of Generalization and Maintenance. The complete guide, plus all 851 practice questions and 3 full exams, is in the study pack and the book.