Ethereum 2.0, also known as Eth2 or “Serenity,” is an upgrade to the Ethereum blockchain. The upgrade aims to enhance the speed, efficiency, and scalability of the Ethereum network so that it can avoid bottlenecks and process more transactions simultaneously.

But Ethereum 2.0 also doesn't really exist—in January 2022, the Ethereum Foundation said it would stop referring to the upgrade as Ethereum 2.0. The rebrand is intended to reflect the fact that what's happening is a network upgrade rather than the launch of a new network. Accordingly, Eth1 is now known as the "execution layer," where smart contracts and network rules reside, while Eth2 is referred to as the "consensus layer," which ensures that devices contributing to the network are acting in accordance with its rules.

The name Ethereum 2.0 has stuck, however.