Interoperability is a characteristic of a product or system whose interfaces are completely understood to work with other products or systems at present or future in either implementation or access without any restrictions.

It may be classified in three main classes:

Syntactic interoperability
If two or more systems are capable of communicating with each other they exhibit syntactic interoperability. Specified data formats communication protocols and the like are fundamental. XML or SQL standards are among the tools of syntactic interoperability. This is also true for lower-level data formats such as ensuring alphabetical characters are stored in a same variation of ASCII or a Unicode format (for English or international text) in all the communicating systems.

Semantic interoperability
Beyond the ability of two or more computer systems to exchange information semantic interoperability is the ability to automatically interpret the information exchanged meaningfully and accurately in order to produce useful results as defined by the end users of both systems. To achieve semantic interoperability both sides must refer to a common information exchange reference model. The content of the information exchange requests are unambiguously defined: what is sent is the same as what is understood. The possibility of promoting this result by user-driven convergence of disparate interpretations of the same information has been object of study by research prototypes such as S3DB.

Cross-domain interoperability
Multiple social organizational political legal entities working together for a common interest and/or information exchange.

https://en.wikipedia.org/wiki/Interoperability