Ruby on Rails, or Rails, is an open-source web application framework written in Ruby that follows the model-view-controller (MVC) architecture.

MVC stands for Model-View-Controller. It is the architectural pattern used by Rails, separating the application into three interconnected components: the model (data), the view (user interface), and the controller (business logic).

Rails uses migrations to handle changes to the database schema. Migrations are Ruby scripts that help developers create and modify database tables and fields.

ActiveRecord is the ORM (Object Relational Mapping) layer of Rails that provides a way to interact with the database using Ruby objects. It simplifies tasks like querying the database and managing relationships between tables.

Rails assets are the files used in web applications, including JavaScript, CSS, and image files. The Rails asset pipeline helps manage and compress these assets to improve performance.

You can create a new Rails application by running the command `rails new my_app` in the terminal, where `my_app` is the name of your application.