Before you start
Read Desktop & Server OS Administration first if "Windows Server" is a new term — this cluster assumes you know what a server is.
CLUSTER 0.2
Before Entra ID, before the cloud, companies still needed one system that knew every employee's username and what they were allowed to touch. That system is Active Directory — and it's still running inside the majority of businesses today, cloud or not.
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Think of it as: the company's master employee directory
One central database listing every user, every computer, and every group in the organisation — and the rules for what each one can access. Almost every login in a Windows-based office traces back to this.
Think of it as: the rulebook that applies itself
Instead of an IT admin manually configuring 500 laptops one by one, Group Policy pushes settings — password rules, wallpaper, blocked USB drives — to every machine in a group automatically, the moment it joins the network.
Think of it as: sorting people into teams so rules can apply to the team, not each person
Rather than granting access file-by-file to 500 individuals, admins put people into groups ("Finance," "Managers") and grant access to the group once. Add someone to the group, they inherit everything it can do.
Entra ID (covered in Cloud & Workplace Orientation) is Microsoft's cloud identity system — but most real organisations run a hybrid setup: Active Directory on-premises, synced to Entra ID in the cloud, so the same identity works in both worlds. You'll rarely find a company that's ripped out AD entirely, even years into a cloud migration.
REAL-WORLD SCENARIO
A new employee joins the Finance team. An admin creates one user account and adds it to the "Finance" group in Active Directory. Group Policy immediately applies Finance-specific software and restrictions to their laptop. By the time they sit down, they can open the shared Finance drive and nothing else — no one manually configured any of it.