What's a URL?

It's simply an website's "address", the one the appears in the white bar at the top of your screen.  As for pronunciation, some people say each initial separately ("you are ell"), and others pronounce it like a word ("earl").  Either is correct.  OR you could impress your friends and call it a Uniform Resource Locator, which is what it stands for. 

For example, the URL for our personal blogs looks like this:

http://rocksinmydryer.typepad.com/

and

http://www.donttrythisathome.typepad.com/