If we create a directory object is an instance of an object class it’s contained in the schema. Every object class contains a list of associated attributes, it’s give the information of the object. Attributes and classes defined independently, so single attribute can contain with multiple classes. All attributes and schema classes are defined by the class schema and attribute schema objects.
There are three types of classes in the schema.
Structural Class – this class is used to objects like (computers and users) in the active directory.
Abstract Class – this class is used to deriving the structural classes
Auxiliary Class – this class contains predefined attributes, it can be include in the structural and abstract classes.
ClassSchema object is used to define the classes in the schema, it provide the template for building active directory objects of the class.
AttributeSchema objects are used to define attributes in the schema. An attributeSchema object determines the allowable contents and syntax for instances of that attribute in the director