The advantage of Proof-of-stake over Proof-of-work for a crypto-protocol is that

		It helps prevent the concentration of cryptocurrency in just a few hands.
		It reduces the amount of computer time required to mine the cryptocurrency.
		It increases the ability of holders of the token to transfer their tokens at all times.
		It increases the use of ASICs in mining the cryptocurrency.

Merge mining is the process by which

		Two different blockchains are simultaneously mined using the same hardware.
		Blockchains such as Ethereum and Bitcoin communicate.
		Miners receive additional Bitcoins for mining coins for other networks.
		Ethereum software is updated to allow proof-of-stake.