Ruby on Rails - a brief overview and intro

I was looking around for PHP implementations of Rails analogues and came across this very simple introduction to Ruby on Rails, by Matt Lightner. Great for those who wonder "what the heck it is and why people are so crazy about it".

He distinguishes between Ruby, Rails, and Ajax, and explains the significance of the latter two, as well as the aggregate technology.

Btw, I found PHP WACT, which appears to do something like Rails.