Consider how questions are asked. Often, when someone asks "what is...", they really mean "Why does it matter to me?" By considering what matters to someone, the answer becomes different and more likely to give them information they can act on.
One of the things that we've learned is that explanation sometimes means answering a different question than was asked. It's not always "what is it?" as much as "why should I care about it?"
The guy who wrote this is Lee Lefever... check him out, he has great videos!
http://www.commoncraft.com/archives/000528.html
They're all made with cut out pieces of paper... are rarely more than three minutes long, and explain complicated technology in perfectly understandable ways. Awesome.
My friend Ariel Hyatt turned me on to this guy... and you simply MUST watch these videos he made... especially the one on RSS... it's genius.
Social Networking in Plain English
http://www.commoncraft.com/video-social-networking
Social Bookmarking in Plain English
http://www.commoncraft.com/bookmarking-plain-english
RSS in Plain English
http://www.commoncraft.com/rss_plain_english
Blogs in Plain English
http://www.commoncraft.com/blogs
Twitter in Plain English
http://www.commoncraft.com
Wikis in Plain English
http://www.commoncraft.com/video-wikis-plain-english