What is Convention over Configuration in Rails?

Convention over Configuration (CoC) means Rails provides intelligent defaults so developers can follow standard conventions and avoid writing boilerplate configuration. For example: a model named User automatically maps to a database table named users, a controller named PostsController has views in app/views/posts/, and a primary key is always id by default. You only need to configure where you deviate from conventions. This dramatically reduces the amount of configuration code and makes Rails codebases predictable and easy to navigate.