what is ruby on rails?
The Language
Ruby is a recent programming language that shares most of its heritage with Perl and Smalltalk. You can see what Ruby looks like (and try it yourself) at tryruby.org.
Just like you can use PHP to write web pages, you can do the same thing with Ruby.
The Framework
Ruby on Rails is a set of software devices that help you to more easily write a website in Ruby. The primary things they try to facilitate ("make easy") are:
- Storing related data (e.g. blog posts and the comments on them) to a database.
- Accepting web requests and respond to them programmatically (e.g. check a user's password)
- Composing HTML using your data, with layouts and templates to make it easier.
"Rails," as it's called for short, is built with extreme prejudice towards certain application models, particularly MVC. What this means is that unlike PHP, where any .php source file is fair game for any bit of code, most code in a Rails application is written in a particular, conventional place. When people compare Rails to PHP, they often point this out.
There's a lot I didn't cover, but these are Rails' most basic features. To see what it looks like, I'd suggest watching the infamous, "Creating a Weblog..." screencast.
If you're looking for something to compare it to for someone coming from PHP, think of it like CakePHP for ruby. It's a bunch of pre-developed low-level classes and systems that can then be extended out to use in many different systems. It also bundles in a lot of other helpful tools and a plugin architecture. It uses ruby and an HTML templating language based on ruby (erb) rather than PHP.
It's a framework for Ruby whose sweet spot is CRUD based web apps. They make a number of assumptions (aka "conventions") that make it easy and fast to create tables with 1:1, 1:m, and m:n relationships, objects, controllers, and web pages for exposing and manipulating that data on the web.
Ruby is just another object-oriented language, like Java, C++, or C#. It was invented by a gentleman from Japan.