Very often people try to edit their audio in the NLE of their choice. They edit the video and then start working on the audio - the problem is that you dont have nearly enough control in SOME NLEs to do this. And this is because SOME NLEs dont allow subframe audio editing. What does this mean?
If you are editing a project at 24 frames per second and cant go subframe for audio then you can only cut or move audio at frame lines which is every 1/24 of a second. While 1/24 of a second sounds short and small, your ear can hear a whole lot faster then that. Take, for example audio recorded at a 48 KHz sample rate - that is 48,000 samples per second - each lasting 1/48000 of a second. Why so much? Cause we hear very very quickly. So to take out an audio pop, or edit a syllable or sibilance or move a word in sync with picture you almost always need a higher audio resolution then the sample rate of your video (24 Hz).
Avid - doesnt allow subframe audio editing so you are forced to export to an audio program, do your work and reimport the results. Adobe CS4 Premier does allow subframe audio editing, down to the sample. FCP allows some subframe editing. ALL audio editing tools allow subframe editing (since they arent really tied to video anyhow).