The Ethereum blockchain consists of the mainnet and the Beacon Chain. The mainnet is secured by proof-of-Work (PoW) consensus algorithm while the parallel Beacon chain, launched on December 1, 2020, uses proof-of-stake (PoS). The Ethereum Merge will take place when the two systems come together, and PoW will be eliminated from the mainnet. Instead of miners, the Ethereum network will be maintained by validators through the staking of ETH. After the Merge is complete, Ethereum will move closer to its vision of being more eco-friendly, scalable, decentralized, and secure.
Ethereum originally planned to put more emphasis on shard chains before the Merge. However, this took a backseat due to the boom of layer 2 scaling solutions, such as Polygon. Ethereum successfully merged on the Kiln testnet in March 2022, in what was seen as a successful proof of concept for the Merge. The difficulty bomb, which will begin the Ice Age and radically increase the difficulty of PoW mining to the level of impossibility, is expected to go off in June or July 2022. At that time, it’s expected that miners will transition to validating under the PoS consensus mechanism.