Rollup
Quick Answer
A rollup is a Layer 2 solution executing transactions off-chain and posting proofs to Layer 1. Optimistic Rollups (Arbitrum) and ZK-Rollups (zkSync) dramatically reduce payment processing costs.
Full Definition
A rollup is a Layer 2 scaling solution that executes transactions off-chain and posts compressed transaction data (or validity proofs) back to the Layer 1 blockchain. Optimistic Rollups (Arbitrum, Optimism) assume transactions are valid unless challenged, and ZK-Rollups (zkSync, StarkNet) use zero-knowledge proofs for instant validity. Rollups inherit L1 security while dramatically reducing fees — making them ideal for high-volume payment processing.