The XML 500 word Challenge

Picking up Mike Champion's question about how to communicate that XML is, so 
it is suggested, "simple" let's have a challenge for list members to explain 
XML in 500 words to someone who is a Web developer but has no formal CS 
training.

Prize: You can polish your XML halo an extra time before going to bed each 
day for week! :)

Seriously, any takers?

Andrew Watt