Stands for Freed/Final Release , indicating a production build rather than a checked (debug) build.
It is commonly used as base media for joining enterprise systems to an Active Directory domain. How to Handle ces-x64frev-en-us-dv9 ces-x64frev-en-us-dv9
It was widely used in testing and deploying virtual machines within Hyper-V. Stands for Freed/Final Release , indicating a production