This is how I know things, so chances are I am wrong to very wrong, but throwing it out there, worst case there'll be laughs and corrections. So well, from my understanding...
The main animator does the keyframes of the animation, and might also fully animate the most important sequences. Then inbetweeners draw some extra frames to make the animation smoother for the scenes of which the animator only did the main keyframes. At this point you don't have a real "animation" yet, since the drawings are on their own, and they are put together and animated at the PC. Once there, generally you get the actual animation done at 7~13fps, with some of the most important scenes that might actually be animated at 23.976 (these things are depending on the budget too). And since this all is put together in NLEs/post-processing software with a 23.976 timeline (or potentially something else, read on), the pans/zooms and other computer-aided effects and animations go at 23.976, whereas the drawings have a lower framerate. That should be how it's done. Then again, depending on the series, you might be getting a VFR thing which has parts going at 23.976, others at 29.97, others at 59.94 (as in, fully interlaced with each field unique), etc... there are many kinds of footage. Luckily these days finding 23.976 progressive on BDs (or 29.97 telecines, on DVDs) seems to be the most common situation, but there still are a few exceptions... which tend to be the hardest and most annoying ones to deal with, especially if there happen to be things going at different speeds in the same sequence (eg: the animation was 23.976, telecined to 29.97, and it has full field interlaced credits rolling at 59.94 on top).
Hopefully I mostly got it right, so now to wait for Hatt to correct the rest...



