Casper?

Hi all,

Doing some research on ETH and stumbled onto a part of the ETH roadmap to 2.0 called "Casper." Seems like Casper is the implementation into ETH that will officially mark the transition from PoW to PoS.

Was Casper rebranded to "The Merge?" I am a bit confused at what Casper is / was / successfully or unsuccessfully happened?

Thanks in advance!