What is Layer 2?
Also called: L2, rollup
A Layer 2 is a network that processes transactions off a base chain such as Ethereum, then posts proofs or compressed data back to it. Users get lower fees while settlement stays on the base layer.
In practice
Optimistic rollups such as Arbitrum and Optimism assume transactions are valid and allow a challenge window. Zero-knowledge rollups post validity proofs instead, so withdrawals settle faster. Base, built on the OP Stack, is the clearest example of a consumer-facing L2. Which model a team picks shapes withdrawal times, bridging risk, and the security assumptions their users inherit.