The long-awaited merge, the purpose of which is to make all Ethereum users happy, commissions low, power consumption even more down, and in general, it's PoS but not PoW. However, "When it's done" and "Merge" have almost become synonymous since the merge did happen, but for now on the Ropsten test network.
Ropsten is the Ethereum oldest test network and has been working since 2016. If you don't know why it's needed, it's like training on ducks first and then going out in public.
What will all this give? An introduction to the developers, how the Ethereum network will work after the switch to PoS, whether everything is ok, etc.