Well what is it? And how do I get involved?
Debugging is a methodical process of finding and reducing the number of bugs, or defects, in a computer program
The Ubuntu QA team "is focused on developing tools, policies, and practices for ensuring Ubuntu's quality as a distribution as well as providing general advice, oversight, and leadership of QA activities within the Ubuntu project."
In general, QA in Ubuntu is divided into the following areas:
The Bug Squad Team "is an essential asset in progressing Ubuntu and its derivatives; The Bug Squad is the first point of contact for the bugs filed about Ubuntu. Members assign bugs to packages, ensure that bug reports are complete, find duplicate bug reports, recreate bugs, and forward bugs to their upstream authors. All of these activities help bugs get fixed and subsequently make Ubuntu even better."
Triaging bugs consists of several things:
Visit these web pages and you can find an easy way to join.
Usually, the term debugging is used by a programmer to refer to the process of investigating why something in their code went wrong and attempting to fix it.
In a broader sense (as I suspect you mean) it can also refer to simply finding bugs in the software that you use and reporting them to the software author.
To be most useful, you probably want to be running cutting edge software (older versions may have the bug that you're about to report, already fixed in a newer version) - this comes with the price that your system will generally be more unstable; but that's what most dedicated bug hunters want, more crashes, more things to report!
Head over to https://bugs.launchpad.net/ubuntu/ to see currently open bug reports - if you find any of your own, create an account and get reporting them! :)