Well of course it matters, that's like saying you've got a poodle but was wondering if it's the same as a bulldog. Sure, they're both dogs but very different.
Ubuntu is probably the most user friendly linux distro you'll get, just about everything is point and click, you get lots of help, no confusing errors and is extremely like windows.
Redhat is pretty friendly too but it uses rpm packages instead of deb packages. Confused? Debian is one of the older linux distros and created the debian package, ubuntu inherited this as it's based on Debian.
Redhat uses its own proprietary package system (rpm) and is a complete pain when you find a closed source proggy that you like and find that it's only available as an rpm.
So yeah Ubuntu will start you off and after a while you'll probably choose to move onto Debian or Gentoo or BackTrack or whatever...