Heh ^ a totally different opinion.
Personally, I played with compressors on the computer for a long time, just messing with the controls. I had a vague idea of what each one did, and I used them to squish and maybe make things louder. None of that experience could replace actually sitting down at uni and reading good detailed descriptions of what a compressor does, and why/when you would want to use it. Obviously, everyone's different