Thinking of Jailbreaking my iPhone 4 - a few questions

Hey guys,

These questions are probably going to seem really noob-esque, but I can't seem to find many answers on the sites I'm looking on. I'm thinking of jail breaking my iPhone 4 - as the title suggests - but just want some clarification on some points:

  • Am I able to return to the stock OS if I decide I don't like my iPhone jailbroken - and if I can, is it as simple as pressing restore to backup on iTunes? I guess the question is relevant to "what happens if it goes tits up, do I simply restore the iPhone to backup prior to jailbreaking it?
  • I have been looking on iClarified, and what is the actual difference between PwnageTool and RedSn0w?
  • I have a seriously low tolerance for jargon, and it's all I seem to come across. I have been looking at RedSn0w for instance, and it talks about tethered and untethered jailbreak - I'm at a complete loss to what that means.
  • Very simply speaking, does jailbreaking allow for access to Cydia, and allows you to install and use third party apps, skins, etc... Am I missing something else?
Yes I'm an idiot, I just want clarification - is that too much to ask?
Thanks for any replies, in advance: they're greatly appreciated.