What is bridging?
In the context of the OP Stack, a deposit is a transaction initiated on the layer 1 blockchain (e g. Ethereum Mainnet) and executed on the layer 2 (e.g. OP Mainnet).
To maintain a shared language, the Superbridge refers to bridge operations where tokens flow from the layer 1 to the layer 2 as deposits, and bridge operations where tokens flow from the layer 2 to the layer 1 as withdrawals.
Deposits and Withdrawals
With rollups the semantics behind deposits and withdrawals are often very different. Deposits are usually finalized quickly, under ~ 10 minutes, and don't require any manual intervention to finalize on the rollup.
Withdrawals are often subject to a 7 day fraud proof delay, and require an extra transaction or two to be finalized on the base chain. For more information on the exact details of this process please see our Optimism withdrawals guide or our Arbitrum withdrawals guide.