Ethereum 2.0 (also known as Eth2 or Serenity) is a major upgrade to the Ethereum blockchain that aims to improve its scalability, security, and sustainability. Ethereum is currently using a proof-of-work consensus mechanism, which requires miners to solve complex mathematical puzzles in order to validate transactions and add new blocks to the blockchain. However, this process is computationally intensive and consumes a lot of energy, which can lead to high fees and slow transaction times.

Ethereum 2.0 will introduce a new consensus mechanism called proof-of-stake, which replaces miners with validators who are selected to validate transactions based on the amount of ether they hold and stake. This reduces the computational resources required to validate transactions and also makes it more energy-efficient, reducing the environmental impact of Ethereum.

In addition to the shift to proof-of-stake, Ethereum 2.0 will also introduce other features such as sharding, which will divide the blockchain into smaller parts called shards to increase its capacity and scalability, and eWASM, a new virtual machine that will improve the efficiency and speed of smart contracts.

Overall, Ethereum 2.0 is a significant upgrade that will make the Ethereum blockchain more efficient, sustainable, and capable of handling a larger volume of transactions and smart contracts.

Ethereum 2.0 is a broad term used to cover several improvements to the Ethereum network, including the switch from proof-of-work to proof-of-stake consensus mechanism. On the other hand, sharding is a scaling solution that will expand Ethereum's capacity to store data and increase the blockchain's computational capacity. Sharding will work in harmony with layer 2 solutions to scale throughput and reduce network fees. While Ethereum 2.0 is expected to launch in September 2022, sharding is expected to come to the Ethereum network in 2023. The Ethereum Merge, which will merge the mainnet with Ethereum 2.0's Beacon Chain, enabling full staking, is a prerequisite for sharding.

According to the provided search results, the Ethereum Merge, which will merge the mainnet with Ethereum 2.0's Beacon Chain, enabling full staking, is scheduled to happen between September 10-20, 2022. After the Ethereum Merge, Ethereum sharding is expected to launch in 2023, increasing the blockchain capacity. However, there is no firm date planned yet for the launch of sharding. It is important to note that the Ethereum Foundation no longer refers to this upgrade as "Eth2" or "Ethereum 2.0".