The execution layer is independent of the underlying data availability and consensus layers, allowing nodes to execute transactions separately and exchange them off-chain, thereby alleviating the pressure on the main network. Through Optimistic Rollup and ZK Rollup technologies, transaction data is sent to the settlement layer (i.e., the mainnet) for final confirmation. The modular inter-layer working mechanism makes the network run more efficiently, development and deployment more flexible, and the network infinitely scalable.

Rollup itself is a type of Layer 2 scaling solution. ZK Rollup stands for Zero-Knowledge Rollup, which refers to rollups using zero-knowledge proofs. Since the process of executing transaction calculations has been moved off-chain, ZK Rollups subsequently send transaction data bundled with zero-knowledge proofs back to the chain, ensuring the validity of the off-chain transaction data without needing to execute on-chain.

Optimistic Rollup refers to an optimistic rollup where the principle is "assume transactions are correct unless proven otherwise." Optimistic Rollups do not submit proofs of transaction validity but instead use fraud proofs. This allows any node to challenge the transaction within a specific time window; if fraudulent activity is detected, the transaction can be contested and removed. This results in better scalability but at the cost of taking more time.

How does the execution layer change the efficiency of blockchain operations?