Ruby on Rails, often referred to as Rails, is a web application framework written in the Ruby programming language. It is designed to make the development of web applications faster and easier by providing a structured environment that follows the principles of convention over configuration (CoC) and the DRY (Don't Repeat Yourself) philosophy.

Here are some key features and concepts of Ruby on Rails:

1. MVC Architecture: Rails follows the Model-View-Controller (MVC) design pattern, which separates an application into three interconnected components. This separation helps in organizing code, improving maintainability and scalability.

   • Model: Represents the data and business logic. It interacts with the database and handles data validation.
   • View: Represents the user interface. It is responsible for displaying data to the user and rendering HTML.
   • Controller: Acts as an intermediary between the Model and View. It processes incoming requests, manipulates data through the Model, and renders appropriate Views.

2. Convention over Configuration: Rails provides sensible defaults and conventions for file structures, naming conventions, and configurations. This means that developers can get started quickly without needing to configure every aspect of the application.

3. Active Record: This is the Object-Relational Mapping (ORM) layer included in Rails. It allows developers to interact with the database using Ruby objects instead of writing raw SQL queries, thereby simplifying database interactions.

4. Routing: Rails provides a routing system for defining how URLs map to controller actions. This makes it easy to handle user requests and direct them to the appropriate processing logic.

5. Gems: Ruby on Rails has a vibrant community and an extensive library of third-party packages known as "gems." These gems can be easily integrated into applications to add functionalities ranging from authentication to payment processing.

6. Built-in Testing Framework: Rails comes with tools for testing applications, which encourages developers to write automated tests and ensure the integrity of their code.

7. Asset Pipeline: Rails includes an asset pipeline that helps manage and serve static assets like JavaScript, CSS, and images, optimizing their performance for production environments.

8. Support for RESTful Architecture: Rails encourages the implementation of Representational State Transfer (REST) architecture, which is a standard for designing web services. This allows for creating more modular and easily consumable endpoints for web APIs.

Overall, Ruby on Rails is known for its emphasis on productivity and developer happiness, making it a popular choice for building web applications of all sizes. It is widely used by startups and large organizations alike for its rapid development capabilities and ease of use.