You can use resources in following three different ways.
resources :users
All the methods in Users controller will have routes defined if you add above line in your routes.rb file. For example users controller have method #index then you will be able to open the url
http://localhost:3000/users.
resources :users, :only => [:show, :new, :create]
If you use the above line in routes.rb then you will be able to just use the show, new and create actions of your controller.
resources :users, :except => [:index, :update, :destroy]
By using the above line you will be able to use any action in your controller execpt index, update and destroy.