Although Optimism is an L2 (and therefore fundamentally connected to Ethereum), it's also a separate blockchain system. App developers commonly need to move data and assets between Optimism and Ethereum. We call the process of moving data and assets between the two networks "bridging".
# Sending tokens
For the most common usecase, moving tokens around, we've created the Standard Token Bridge. The Standard Token Bridge is a simple smart contract with all the functionality you need to move tokens between Optimism and Ethereum. It also allows you to easily create L2 representations of existing tokens on Ethereum.
# Sending data
If the Standard Token Bridge doesn't fully cover your usecase, you can also send arbitrary data between L1 and L2. You can use this functionality to have a contract on Ethereum trigger a contract function on Optimism and vice versa. We've made this process as easy as possible by giving developers a simple API for triggering a cross-chain function call. We even use this API under the hood (opens new window) inside the Standard Token Bridge.