@TechQ, Thanks for posting in Q&A. In General, Microsoft Intune is a cloud service which manages user access and simplifies app and device management across your many devices, including mobile devices, desktop computers, and virtual endpoints. For example, you can manage device via device configuration policies, manage app via app configuration policy or protect organization data on app via app protection policy and etc.
Also, Microsoft Intune can integrate with other Microsoft products and services, like Microsoft Defender for Endpoint to help enterprises prevent, detect, investigate, and respond to threats. Here is a link with more details:
https://learn.microsoft.com/en-us/mem/intune/fundamentals/what-is-intune
In addition, for windows, currently windows server is not supported to be managed by Intune. Only Windows client can support. To know the supported OS, you can read the following link as a reference:
https://learn.microsoft.com/en-us/mem/intune/fundamentals/supported-devices-browsers
If you just want to use Window defender, Intune is not necessary. But if you want to deploy settings for Microsoft Defender for Endpoint on devices you manage with Intune, you can consider Microsoft Intune and configure integration of Microsoft Defender for Endpoint with Intune
https://learn.microsoft.com/en-us/mem/intune/protect/advanced-threat-protection-configure
Hope the above information can help.
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