Ruby on Rails is an open-source full-stack web application framework developed by David Heinemeier Hansson, initially for the Basecamp application. It emphasizes principles like DRY (Don't Repeat Yourself) and convention over configuration, facilitating rapid application development with extensive support for testing, code generation, and various database systems. Supported by companies such as Google and IBM, Ruby on Rails runs on multiple platforms including Linux, Windows, and macOS.