Ruby is an object oriented programming language. Which was made in Japan by Matz in the 90's. It's been slowly getting speeding here, while being extremely popular in Japan, and recently it blew up in U.S. when D.H.H. - a programmer with a Messiah complex (and good ideas) - made a framework for Rails so that he could make Ruby apps quicker and easier. Thus Ruby on Rails was born.

http://www.rubyonrails.org
Run by D.H.H. - made Rails while working with 37Signals. They made BaseCamp and CampFire and those small business apps that are taking off.

It's not any kind of PHP. It is it's own Language + Framework. Just as PHP has Cake -> Ruby has Rails.

It's supposed to be the programmers, programming language. If that makes any sense. Check out the site if interested. It's all open-source and free.