Synapse is an interoperability protocol that facilitates secure and seamless communication between different blockchains. It comprises three main components: generalized cross-chain communication, an optimistic security model, and a Synapse bridge. With the generalized messaging system, any data, including smart contract calls, can be sent across chains, allowing for universal blockchain composability. This eliminates the need for deploying applications separately across multiple blockchains, creating a centralized application layer.