You could have tried that yourself.. just take a look at what happens when you import 24fps footage into a 99fps compilation.. by default it will just insert extra duplicate frames..
You can also interpret footage blabla.. you can find it in the help file:
So basically, it will always try to keep audio in sync with video by adding duplicate frames, unless you change the frameduration stuff yourself. Looks all very normal in AE.
There is also an option for frame blending stuff.. can come in handy with NTSC to PAL stuff (Never used it, never used the pulldown interpretation either). Again.. from the help:
You won't see it in AE when pre-rendering (at least i didn't), but when rendering it to a video file you will see weird stuff when you enable pixel motion (that means it works), same goes for Frame-Mix I guess..
(you can also see how it looks by slowing the video down -that is in a comp that has the same framerate - and let timewarp do the pixel motion stuff. You can look that timewarp stuff up yourself if you want to)
Anyway.. Try searching in the help some more.. you can find a lot of information there..