What is Windows 10 Enterprise E3/E5 on CSP?

The Windows 10 Enterprise E3/E5 licenses CSP are add-on licenses that enable  users to upgrade from Windows 10 Professional to Windows 10 Enterprise. This enables the user to leverage those additional features that come with Windows 10 Enterprise such as Credential Guard, Device Guard, Applocker, Application Virtualization  Managed User Experience for E3 and E5, and Windows Defender Advanced Threat Protection that also come with E5.

 More details about Windows 10 Enterprise can be found here.