Compression reduces the amplitude of louder waves in a track. It's handy when you've got a track that varies substantially in volume; applying compression makes the track (or selection) sound "tighter."
I use compression often, but sparingly. You might find it handy on guitar and vocal tracks - but beware of polluting your mixes with too much crap.
You can certainly read about equalizers anywhere. Do a search for EQ or equalizers, and you'll get tons of returns. What I'll say here is that EQ is extremely important. The fuzziness that you're talking about might be alleviated through proper use of the EQ. For instance, the last thing I do when mixing vocals, is stick a 4 band EQ on the track - and bring the treble and low-mid up. Treble, on vocals, makes the voice sound like it's right next to you - but overdoing it makes it sound like you've got a bad cold. Similarly, you'd want to accentuate lows on a bass track, or mids on a guitar solo, etc.
The best solution: play with the EQ, play compression, play with reverb..play with it all until you get a sound that makes you tingle.
If you don't get a sound that makes you tingle, go buy some of that special cream. So long as you tingle, that's what's important.
