Apple ID - what is it for, and can I safely ignore it

Question

My wife recently bought an iPad (about six months ago). I guess she registered it or something, because every few weeks she receives an email asking her to verify her Apple ID. None of the links in the email work (no matter what email readers she views it in) and she is quite worried about it - that the warranty may be void or something because she can't 'verify' it.
She asked me to look into it - and I must say I can't figure out what an Apple ID is either, or why I need one (I think I must have one to make this post).
Our business owns quite a few Apple products (iphones, several Mac computers, various iPods etc) and I can't recall (aside from posts like this) ever having used an Apple ID for anything. My guess is that with most of the computers we don't have one.
Are we missing on out anything that matters by just ignoring the Apple ID issue? Does it void the warranty or something?
Cheers

Answer 1

They aren't asking for my Apple ID, they want my wife to 'verify' the email address she registered with - but the links they send don't work, and they don't provide a URL (often emails sending links will also provide a URL to copy and paste if the link doesn't work).
We have bought various iPhone and iPad apps using the App Store on the gadgets themselves, and the other day I bought some software through some kind of Mac App Store (sorry - might have the name wrong). I would much prefer to buy software directly on-line from the company which makes it, but this package wasn't available except through the Mac thing. Makes keeping track of receipts etc. much harder.
I find iTunes very confusing to use - not intuitive at all. I don't listen to music. I don't buy it (or any of the other stuff) but I do need to manage my iPhone (it is forever having technical glitches which requires me to re-set it to defaults etc, plus I need to sync the calendars etc.)
It actually took me about six months to work out that iTunes had anything to do with my iPhone - I knew there had to be some way of doing upgrades etc., but it never occurred to me to look for it in a music sales program that I never use.
Yeah. I know. My daughter tells me I'm a silly old **** and a technophobe. But it's me (not her) that makes the purchasing decisions...