Ethereum 2.0, being a major upgrade to the Ethereum network, is meant to improve ethereum's performance and increase its usage. In Ethereum 2.0, Proof of Stake mechanism will implemented replacing its current Proof of Work mechanism.

Proof of Work mechanism has been widely used in most block chain such as Bitcoin, Litecoin etc. Through mining, blocks are being mined by solving complex mathematics problems. Miners are rewarded for successful blocks mined. The cost here are the computational energy used the run nodes for the mining process. In order to achieve this, hardwares and electricity are the major parts in determining miners' profitability. The Proof-of-Stake consensus mechanism will be able to eliminate expensive mining costs.

Another feature, which is Sharding, will be able to increase the speed of transactions by dividing the blockchain into different chains. Hence, multiple transactions can be processed simultaneously.

Ethereum 2.0 is expected to launch in phases in July 2020 . However, it will only be fully functional in Phase 2. Until this period, the current blockchain will continue exist.

Reference:

https://consensys.net/blog/blockchain-explained/what-is-ethereum-2/