[Keyframe]

baking, in this context is a stream of vertices where each frame carries geometry information and nothing else.

If geometry wasn't baked in, then you would have a separate description of geometry (and everything else) as well as keyframes which are left to the client to interpolate.

Think of it as a HTML versus a screenshot. Both carry the same information, but for screenshot you don't need anything else apart from image viewer. For HTML you need parser, layout, render, whatever.. poor analogy, but hey.

USD is a next generation RIB, like OSL (done at sony) is next gen RSL. Both RIB and RSL stem from RISpec https://en.wikipedia.org/wiki/RenderMan_Interface_Specificat... which is a good intro to see what's being talked about here.