Can someone please explain to me the framework behind websites like Odesk, Elance etc ?

I'm basically trying to learn how to create a simple website which uses the same methodology: Users create a priofile or account, and other users can avail services and rate them. Or even connect to them on some level. Specifically I would like to know what programming languages or tools can be used to build it.

I have a background in coding, and have just finished learning the basics of Javascript, Jquery and currently learning Ruby on Rails. I'm looking for ways to better hone these new skills.