Interoperability allows separate systems to communicate and make meaningful use of exchanged information. In crypto, it can describe compatible wallets and applications on one network or communication between blockchains with different execution and consensus systems.
Shared interfaces are one layer
A token standard gives applications a common way to query balances or request transfers. This reduces integration work, but matching interfaces alone does not synchronize state between chains. Two networks can run compatible smart-contract code while maintaining entirely separate balances and histories.
Messages across chains
Cross-chain protocols add ways to transport messages and verify their origin or authorization. IBC, for example, separates message transport and verification from the application logic that interprets a transfer or instruction. The actual verification model matters; it may involve light clients, proofs or other configured trust assumptions.
Successful delivery is not enough
Both sides must agree on asset identifiers, message meaning and failure handling. Finality delays, unavailable relayers, contract bugs or compromised verification keys can interrupt the process. A bridge interface connecting many networks does not imply that all routes have equal security. Assess interoperability by the specific operations supported and the conditions under which the receiving system accepts them.