What do the terms tree, forest, domain, schema and domain controller refer to in Active Directory?

 In Active Directory, if a collection of domains are arranged in a hierarchy and share a namespace, they are collectively referred to as a tree. A collection of trees is referred to as a forest. Trees within the same forest may share many attributes and resources, like directory schema and configuration, global catalogue and logical structure. When you create a class object in a forest, the schema is the component that provides a definition to the object. It creates and stores the rules, attributes and references for objects in the Active Directory database. Schema can be interpreted as a type of working drawing that creates different components together through well-defined properties, functions and relations.

A domain controller keeps the Active Directory database running during operations. It authorises and authenticates users based on the information in a particular database. Domain controllers are also responsible for replicating data across Active Directory databases.