GeoServer data directory - GeoServer 2.17.x User Manual
The GeoServer data directory is the location in the file system where GeoServer stores its configuration information. The configuration defines what data is served by GeoServer, where it is stored, and how services interact with and serve the data. The data directory also contains a number of support files used by GeoServer for various purposes.
https://docs.geoserver.org/latest/en/user/datadirectory/index.html