Three letters after "Computer-Aided," three completely different questions: what is this, how do I make it, and will it actually work.
Because CAD, CAM, and CAE all sit in the same software category and often live inside the same suite (Fusion 360 and NX both bundle all three), it's easy to think of them as tiers of the same tool — CAD for beginners, CAM and CAE for "advanced" users. They aren't tiers. They are three unrelated questions applied to the same geometry: CAD (Computer-Aided Design) defines what the part is — its shape. CAM (Computer-Aided Manufacturing) figures out how a physical machine produces that shape. CAE (Computer-Aided Engineering) predicts how that shape will behave under real-world loads, flow, heat, or vibration before anything gets cut.