PostGIS is a spatial database extender for PostgreSQL (https://www.postgresql.org) object-relational database. It adds support for geographic objects allowing location queries to be run in SQL.
It adds several geographical features on top of PostgreSQL such as extra types for geometry, geography, raster, and a few others. For this application, the geospatial support that it provides is relevant. However, readers are advised to explore this extension in depth in case they are going to be dealing with the PostgreSQL database.
