GeoPackage is an open, SQLite-based file format for storing geospatial data,
including vector features, raster tiles, and related metadata, in a single
portable .gpkg file.
Because it is built on SQLite, a GeoPackage is both a file and a small relational database. It can store tables, indexes, metadata, coordinate reference system information, and spatial data in one portable artifact.
The main use case is exchanging GIS data without needing a running database
server. A .gpkg file can be copied, attached, archived, emailed, or opened by
GIS tools while still preserving structured geospatial data better than loose
collections of files.
GeoPackage is often a better interchange format than older shapefile-based workflows because it avoids spreading one dataset across several sidecar files, supports longer names and richer metadata, and can hold multiple layers in one file.
It is not a replacement for a server database such as PostgreSQL with PostGIS when many users need concurrent writes, permissions, APIs, backups, and operational controls. It is better understood as a portable geospatial container.