Real-world entities such as users, computers are represented as objects in Active Directory. Objects are the fulcrum for the very existence of Active Directory. One important aspect with respect to object characteristics is that some of the objects can contain other objects. On a broader sense, objects that contain other objects are container objects while others are just leaf objects.
Each object consists of a set of attributes which best describes it. For example, consider a user object. A user is described by attributes like Name, Address, Telephone number and so on. Active Directory supports numerous types of objects. To unambiguously identify an object, a global unique identifier is associated with it. The objects that can be authenticated and to which permissions can be assigned are called as security principals. Each security principal object has a security identifier associated with it in addition to the global identifier. User, computer and group objects are referred to as security principal objects.
Active directory supports various types of objects like User, Group, Contact, Computer, Shared Folder, Printer and Organizational Unit. Some of the object types are explained below.