For our purposes JSON is a string that can be easily stored in a file, or can be easily transmitted over some networking protocol. This makes it an extremely useful format for data exchange between processes even if the process are running on different machine, at different times, and are written in different languages. It can be also used as a format for configuration files as it is rather readable and writable to humans as well.
Use cases of JSON
Using it as a human edited configuration file is another use case. The fact that it allows the creation of deep hierarchies makes it much more useful that the INI-file format which was used extensively especially in Microsoft Windows.
JSON can be used as a Data Serialization method for caching.
Implementations and articles