First, please direct Rails questions to the Rails list. You'll usually
get better help there than here.
http://www.google.com.au/search?q=rails+mailing+list
Secondly, you're looking for config/routes.rb. Reading the comments will
probably tell you all you want to know. You can check out the Routing
manual for more info.
http://manuals.rubyonrails.com/read/chapter/65
Cheers,
Dave