If you're like me and have been hidden under a rock when it comes to browsers, here's how tabbed browsing works. You group a set of websites in a folder (much like managing bookmarks in IE), then you drag that folder into your "bookmarks toolbar." For instance, I have a "news" folder with MSNBC, CNN, and the BBC inside. I can open all those sites at once, and they appear as tabs that I can click to.
If you're wondering how it looks, here's a link to a screenshot (just the very top of the browser window is shown):
screenshot
The coolest thing about this is that the other pages in the folder load while you're just viewing one of them. So instead of opening five or six sites separately, they all open at once, and you can just tab back and forth. So I can view my regular websites (about forty of them daily) much more quickly, with much less waiting.
It's very intuitive and very easy to use. Pages also seem to load significantly faster than when using IE. And there's the security advantage, since eight million people aren't sitting around writing Firefox exploits as a hobby.
I'm really pleased with the switch and only wish I'd done it sooner.