Is there an introductory page here, like the "New To Kitchens?" page on the kitchens forum? I haven't found it.
Well, there's mongo's famous FAQ:
Here is a link that might be useful: FAQ/Bathroom Plumbing for Dummies
If you're considering a remodel or new build for a bath you might want to read this, too.
Here is a link that might be useful: Best bathroom decisions thread