What is Active Directory?

Active Directory (AD) is a hierarchical structure that stores information about objects on a network, built into Microsoft Server.

Basically AD determines will determine what a user will be allowed to do on a computer that's on a domain. Familiar with logging onto a Microsoft computer with a username and password? Yeah, AD will be authenticating this request and will determine whether your eligibile to login or not. AD can be configured to determine email accounts, file shares, websites, telephone numbers - you name it - AD will store it!