Rails is a full-stack, open source web framework that enables you to create full-featured, sophisticated web-based applications, but with a twist... A full Rails application probably has less total code than the XML you'd need to configure the same application in other frameworks.
You'll see how easy it is to install Rails using your web server of choice (such as Apache or lighttpd) or using its own included web server. You'll be writing applications that work with your favorite database (MySQL, Oracle, Postgres, and more) in no time at all.
You'll create a complete online store application in the extended tutorial section, so you'll see how a full Rails application is developed — iteratively and rapidly.
Rails strives to honor the Pragmatic Programmer's "DRY Principle" by avoiding the extra work of configuration files and code annotations. You can develop in real-time: make a change, and watch it work immediately.
Forget XML. Everything in Rails, from templates to control flow to business logic, is written in Ruby, the language of choice for programmers who like to get the job done well (and leave work on time for a change).
Rails is the framework of choice for the new generation of Web 2.0 developers. Agile Web Development with Rails is the book for that generation, written by Dave Thomas (Pragmatic Programmer and author of Programming Ruby) and David Heinemeier Hansson, who created Rails.