What do I need to know before my Android Welcome Party?

Hello.

So, I'm new here, but not too new to figure out how heated things can get in the different forums. A little introduction then, shall we? I'm an Apple enthusiast - BIG one. All the same, I can't pretend not to notice how the Android OS has come along in leaps and bounds, while iOS seems to have, err, stagnated somewhat. Which brings me to my big announcement: I have decided to get an Android phone.

Two reasons: One, the reviews and experiences I've read and heard from users, especially post-ICS, have drawn me in. Two, I've realised how much I'm tied to using Google's apps even on iOS, so I might as well, right? The one thing I still don't quite understand about Android is when I see the terms, "custom ROM", "CyanogenMod", "rooting", etc. As an iOS user, I've just recently sworn off jailbreaking because of the instability it brings, albeit little. Is installing a custom ROM the same as rooting, and are both of them analogous to jailbreaking? And if I stay away from doing either on my new Android phone, most likely the Nexus 4, am I going to miss much in terms of overall experience of the wonders of Android?

I'd appreciate your honest opinions based on your different experiences. Many thanks.