Base is a layer-two chain developed by Coinbase. It is built on Optimism, a layer-two scaling solution for Ethereum — and the second largest L2 ecosystem, behind Arbitrum. Optimism aims to solve the blockchain trilemma by providing interoperability and composability for participating rollups, one of which will be Base.
Optimism's long-term goal is to develop into a "superchain" of L2 chains, with the aim of facilitating the scaling of Ethereum. This superchain introduces a shared security model and tooling for developers to create and interact with Optimism-compatible layer 2s, enabling all chains to work with a normal wallet. Read: How To Add Optimism To Metamask
Coinbase has been working with Optimism for over a year and contributed to developing EIP-4844, also known as proto-danksharding, which aims to increase block space and lower gas fees. This upcoming Ethereum upgrade can decrease L2 transaction fees by 10-100x. Launching multiple L2 rollups may replace multiple L1 chains, which could lead to a bullish dynamic for Optimism and projects associated with it.