Ethereum 2.0, also known as "Eth2" or "Serenity," is a major upgrade to the Ethereum blockchain, aimed at improving its scalability, security, and sustainability. The most significant change in Ethereum 2.0 is the transition from a Proof of Work (PoW) consensus mechanism to Proof of Stake (PoS).

In the current PoW model, miners use computational power to solve complex cryptographic puzzles to validate transactions and add blocks to the blockchain. This process consumes a significant amount of energy and resources. With Ethereum 2.0’s PoS model, validators are chosen to create new blocks based on the amount of cryptocurrency they hold and "stake" rather than competing through power-intensive mining.

This shift will effectively end traditional Ethereum mining, as PoS doesn't require the use of hardware such as GPUs or ASICs. Miners who previously relied on Ethereum for profits will need to transition to staking, mine other cryptocurrencies, or repurpose their equipment.

The PoS model is expected to reduce Ethereum's energy consumption by over 99%, address concerns around environmental impact, and enhance network scalability by allowing more transactions per second. Ultimately, Ethereum 2.0 will transform how the Ethereum network operates and how participants earn rewards.