What contains the rules and definitions that are used for creating and modifiying objects classes and attributes within active directory?

The rules and definitions for creating and modifying object classes and attributes within Active Directory are contained in the Active Directory Schema. The schema defines the types of objects (such as users, groups, and computers) and their attributes, as well as the relationships between them. It can be modified using tools like Active Directory Schema snap-in or Windows PowerShell, allowing administrators to customize the directory according to organizational needs. Changes to the schema are critical as they affect how data is stored and accessed within Active Directory.