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Active Record is the Object-Relational Mapping (ORM) layer in Ruby on Rails. It allows developers to interact with the database in an object-oriented way. Here are some key features and concepts of Active Record:
1. Mapping between tables and classes: Each table in the database maps to a class, and each row in the table maps to an instance of that class.
2. CRUD Operations: Active Record provides methods for creating, reading, updating, and deleting records without needing to write raw SQL.
3. Migrations: It allows for database schema changes to be managed via Ruby code, making it easier to evolve the database schema over time.
4. Associations: It supports defining relationships between different models (e.g., `belongs_to`, `has_many`, `has_one`, `has_and_belongs_to_many`).
5. Validations: Active Record provides a way to define constraints and validations for data before saving it to the database.
6. Callbacks: It allows executing custom code before or after certain events, like saving or updating a record.
Active Record simplifies database interactions and integrates seamlessly with Rails applications.