Since you know the Ubuntu name, it's as good a place to start as anywhere.
Agree with Bushfiva here.
Ignore what people like seacue tell you about their preference for some minor linux distro that nobody's ever heard of.
Why ? Because you're a beginner. You want a well supported distro with a bit of history behind it... Ubuntu has been around for a while now, you'll have no difficulty finding people in the community to hold your hand (whether on here, the "official" Ubuntu forums or elsewhere)... and there's little risk of Ubuntu being abandoned as a project any time soon.
Basically now is not the right time to start choosing your distro.... you can do that later. For now, you want the biggest and most widely adopted you can find. Ubuntu, Fedora and SUSE are the "big three" .... and probably in that order as well.
Now seacue will probably come back here and try to tell you how MINT is "based on Ubuntu"... but the fact is the further you go away from the source, the more quirks and individual ways of doing things you introduce to a system.... which is something a beginner really doesn't need to deal with .... once you've cut your teeth on one of the main distributions,
then you can poke around the smaller distros and see if they suit you better.
As for where to start ? Well, its Linux ... so to some degree you're going to have to jump in on the deep end and accept the learning curve that you've taken on, its not particularly difficult on Ubuntu, but there are many things that Linux does differently to Windows, and it all depends how deeply you want to get into it (i.e. whether you wish to acknowledge the presence of a command line and the "real" operating system behind the pretty GUI). Maybe the link Bushfiva suggested, maybe one of the "For Dummies" books....or maybe just pure luck and solid determination ...... whatever suits your learning style.