Windows Server licensing can feel confusing because it combines server cores, edition rights, and Client Access Licenses. This guide explains the basics so you can choose the right license before you buy.
Core licensing
Windows Server is generally licensed by physical processor cores. Check the edition and core count you need before purchase.
CALs
Client Access Licenses may be required when users or devices connect to the server. User CALs are usually best when one person uses multiple devices; Device CALs can fit shared workstations.
Standard vs Datacenter
Standard suits many smaller deployments, while Datacenter is designed for heavier virtualization needs.