Active Directory (AD) is Microsoft's directory service for managing users, computers, permissions, and other resources within a Windows network. It provides administrators with a centralized way to authenticate users, control access to resources, apply security policies, and manage devices across an organization.

A backend server is a server that handles the behind-the-scenes processing required by a website, application, or online service. It receives requests, executes application logic, communicates with databases or other services, and returns the required data to the frontend.

Backup retention refers to how long backup copies are kept before they are deleted, overwritten, or moved to long-term storage.