what's the difference in jailbreaking and unlocking an iPhone?

I have a 1.1.4 version iPhone and would like to install 3rd party apps on it but the ones I want say I have to have a unlocked or jailbroken phone. I don't want to switch carriers I just want to have more choices and freedom than I have now. Is it possible to do any of that without voiding my warranty if theirs a problem? How hard is it to do? I looked at the instructions for both and it looks way confusing!! Mind you I am new at the whole computer thing I got my first computer 3 months ago! never having even turned one on before that…. can anybody help me and if you can with step-by-step instructions. It took me a month to figure out how to put a movie into iTunes and sync with my phone and that's after someone from this site finally helped me. thank you…,!