xecution layer: Transactions and state changes are first processed here. Typically users also interact with the blockchain through the execution layer, including signing transactions, deploying smart contracts, and transferring assets.

Settlement layer: The settlement layer is used to verify the execution result of the rollup and resolve disputes. It does not exist in a monolithic chain and is an optional part of a modular stack. By analogy, for the US court system, the settlement layer is like its Supreme Court, providing final verdicts on disputed issues.

Consensus layer: The consensus layer of the blockchain downloads and executes the contents of blocks through a full-node network, reaching consensus on the validity of state transitions, thereby providing ordering and finality.

Data Availability Layer: The data needed to verify the validity of state transitions should be published and stored in this layer. In the event of an attack where malicious block proposers withhold transaction data, these data can be easily verified. The data availability layer is the main bottleneck in the impossible triangle of blockchain scalability, which we will explore later.