Windows Server 2025 licensing is primarily based on the number of physical cores on a server, so each "additional core" represents one more processing core you can use.

Additional Cores may be purchased at two times: Point-of-Sale (POS) which refers to purchasing at time of purchase of Windows Server 2025 Standard Edition; or After Point-of-Sale (APOS) which refers to purchasing *after* purchase of Windows Server 2025 Standard Edition

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In Microsoft Windows Server 2025, an "additional core" refers to a single processing core beyond the minimum required license, which is typically based on the number of physical cores on a server, meaning that if you purchase an "additional core" license, you are essentially paying for the right to utilize one more processing core on your server for running Windows Server workloads; this licensing model is used to scale up the processing power needed for demanding applications.