Data stored within Active Directory is presented to the user in a hierarchical fashion similar to the way data is stored in a filesystem. Each entry is referred to as an object.
At the structural level, there are two types of objects: 1) containers and 2) non-containers. Noncontainer objects are also known as leaf nodes. One or more containers branch off in a hierarchical fashion from a root container.
Each container may contain leaf nodes or other containers. As the name implies, however, a leaf node may not contain any other objects. Although the data in Active Directory is presented hierarchically, it is actually stored in flat database rows and columns. The directory information tree (DIT) file is an Extensible Storage Engine (ESE) database file. This answers the question
Does Active Directory use JET or ESE database technology?
ESE is a JET technology
Consider the parent-child relationships of the containers and leaves in Figure 2-3. The root of this tree has two children, Finance and Sales. Both of these are containers of other objects.
Sales has two children of its own, Pre-Sales and Post-Sales. Only the Pre- Sales container is shown as containing additional child objects. The Pre-Sales container holds user, group, and computer objects as an example.