I’m confused by the term &

I’m confused by the term "balanced" in microphone terminology. At first I thought it meant a stereo microphone. Now it’s obvious from reading that it is not.

I use an AT 822 mic (stereo) with an XLR-to-1/8" adapter. When I record to MiniDV, I get a stereo track. I also get this using the same setup into my Mac soundcard. I thought it was the XLR that was stereo- but it’s the adapter.

So, can anyone out there explain what exactly "balanced" means, and why it’s a big deal?

Also, if I want to record to a cam like the Canon XL2, do I need a Y adapter to two XLRs to get my stereo?

Thanks in advance.