You can see : Windows Server 2012 R2: What Does “Extended Support” Really Mean?
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Extended support refers to the latter 5 years of product support per the LTSC system. It’s no longer the focus of the Microsoft team, and will likely have been succeeded by at least one more product in the meantime. During extended support, customers will only receive critical security updates and reliability patches. Non-security hotfixes will not be delivered unless the customer has an extended support agreement with Microsoft – and that comes at a cost.
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