Ethernal has three main use cases 1. Individual contributors Developers can spin up a full block explorer connected to their local development chain in a few minutes. Blocks & txs are automatically synced and processed, and give detailed info to the developer. ABIs can also be synced in order to generate an UI to interact with the contract. 2. Teams Through either the UI or the API, teams can connect their hosted testnet RPC and get a full explorer accessible through a public url (can be their own domain), making easier to do internal/user testing. 3. Appchains It can be block explorer for Optimism L2s. It takes a few seconds to launch and everything is handled automatically. It has an API to launch explorers on demand (especially important considering all the "L2 as a service" launching).