Generators are used to help produce “out of the box� code for use in a Rails program.
When you run the generator (using script/generate) new files (controllers, models, views, etc) are generated and added to your application.
Generators often install just the minimum code necessary to get you started. You are usually expected to edit this code to have it do what you want. For ‘drop-in’ functionality, you may want to check out Plugins, Rails Engines, 3rdPartyLibs and/or 3rdPartyHelpers.
See AvailableGenerators for a list of available generators.
There is also a WishList available.