Polygons are used delimit geographical areas. Mapping polygons on a geographical map, or Polygon Mapping, provides essential foundations for combining place-based data and information.
Where coordinates indicate a precise geolocation (points), polygon maps delimits areas (spaces). See Polygon 
.
Further geolocation-based data can be linked to polygon-mapped areas. For example for the purpose of Farmland Mapping.
Polygons can be mapped on the basis of geographic maps, satellite images, or through walking, biking or driving while identifying points visited and connecting them into polygon maps. Special toos are available to do this.
I like to think of Polygon maps as graphable and Knowledge Graphs too: they are a set of topological coordinates and the area enclosed by them.
See also:
Guidance on the Collection of Polygon Data , Iseal Alliance, 2020.
QGIS , a free and open source Geographic Information System.