ETH Layer2 uses Rollups to package hundreds of transactions into one submission to the Ethereum mainnet, thereby the transaction fees will be divided to all Rollup users, reducing fees per user. Transaction data in the Rollups is submitted to Layer1, but executions are carried out independently by the Rollups. By submitting transaction data to Layer1, Rollups can inherit the security of Ethereum because once the data is uploaded to Layer1, rolling back Rollups transactions requires the data to be rolled back on Layer1.