The "Serenity" update (Ethereum 2.0) is a comprehensive transformation of the Ethereum network to shift from a "mining" (Proof-of-Work) system to a "staking" (Proof-of-Stake) one, and to implement a "sharding" architecture.

These changes aim to make Ethereum a much faster, more efficient, cost-effective blockchain platform capable of supporting a large number of users and decentralized applications on a global scale.