When two programs need to exchange data they need to agree a common format for the data in transit. This could be a binary format, or it could be some sort of human readable text.
The binary format could be defined by one of numerous pieces of middleware, or a public format such as Google Protocol Buffers. The text format could be one of the titans of data formats: XML or JSON. Or it could be something more old-fashioned, like comma separated values (CSV).