What is needed to get clear from the start is that every compressor will sound different, the controls will act differently, and some will be better at doing certain types of compression than others. While the basic controls like ATTACK and RELEASE will have a similar function, the resulting change to the sound may be totally different.
David from www.learndigitalaudio.com has made a deep and comprehensive article about compression and ThrillseekerLA. Don’t miss to read the whole thing over there at his site which contains lots of examples and explanations. Theres also a PDF document available.