A simple search in Google provides a lot of information. Also wikipedia
http://en.wikipedia.org/wiki/Scaffold_(programming)
Long story short a scaffold is simply a utility that most MVC web frameworks provide to create the necessary code/files for simple CRUD operations in the application.
In Rails, this means it will create the following from bottom up:
Active Record/Models
Migrations: These are used to create the necessary tables/columns for the model.
Models: Self explanatory, class of the model that subclasses from ActiveRecord::Base
Resource Routes
- resources: :model: It generates the CRUD routes:
index
, show
, new
, create
, edit
, update
, destroy
by placing the resources: :model_name
line in the routes.rb
file.
ActionController
- Controller: The controller that ties in the routes with the models and views with necessary code to perform the CRUD operations.
ActionView
Views: The views that display a very simplistic UI for performing the CRUD operations.
Assets: The javascripts, images, css, that are used in the views. This is very modular thanks to the assets pipeline.
It creates a bunch of other stuff based on your choices of test libraries. You can actually see what it's doing by just running rails scaffold SomeModel
.