Description of Contents
The default directory structure of a generated Ruby on Rails application:
app Holds all the code that's specific to this particular application.
app/controllers Holds controllers that should be named like weblogs_controller.rb for automated URL mapping. All controllers should descend from ApplicationController which itself descends from ActionController::Base.
app/models Holds models that should be named like post.rb. Models descend from ActiveRecord::Base by default.
app/views Holds the template files for the view that should be named like weblogs/index.html.erb for the WeblogsController#index action. All views use eRuby syntax by default.
app/views/layouts Holds the template files for layouts to be used with views. This models the common header/footer method of wrapping views. In your views, define a layout using the layout :default and create a file named default.html.erb. Inside default.html.erb, call <% yield %> to render the view using this layout.
app/helpers Holds view helpers that should be named like weblogs_helper.rb. These are generated for you automatically when using generators for controllers. Helpers can be used to wrap functionality for your views into methods.
config Configuration files for the Rails environment, the routing map, the database, and other dependencies.
db Contains the database schema in schema.rb. db/migrate contains all the sequence of Migrations for your schema.
doc This directory is where your application documentation will be stored when generated using rake doc:app
lib Application specific libraries. Basically, any kind of custom code that doesn't belong under controllers, models, or helpers. This directory is in the load path.
script Helper scripts for automation and generation.
test Unit and functional tests along with fixtures. When using the rails generate command, template test files will be generated for you and placed in this directory.
vendor External libraries that the application depends on. Also includes the plugins subdirectory. If the app has frozen rails, those gems also go here, under vendor/rails/. This directory is in the load path.