Ceramic is a decentralized event streaming protocol that enables developers to build decentralized databases, distributed compute pipelines, and authenticated data feeds, etc. Ceramic nodes can subscribe to subsets of streams forgoing the need of a global network state. This makes Ceramic an eventually consistent system (as opposed to strongly consistent like L1 blockchains), enabling web scale applications to be built reliably.
The protocol doesn't prescribe how to interpret events found within streams; this is left to the applications consuming the streams. One example of this type of application is ComposeDB.