GET/POST/PUT/DELETE

I trying to understand the purpose of each request of GET/POST/PUT/DELETE, generally we are using those in routes.rb of our Rails App. I need exact explainition with example of each one in Rails app.

http://en.wikipedia.org/wiki/Restful#Concept http://en.wikipedia.org/wiki/Hypertext_Transfer_Protocol#Request_methods

http://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html