Geoshape is the polygon or line data stored in the OpenStreetMap database, identifiable by Wikidata ID. It allows MediaWiki-extensions-Graph and Maps to draw overlays without storing the raw data on wiki.
Largest use case is Wikivoyage, where it could replace GPX stored in wikipage and help migration of Wikivoyage to maps.wikimedia.org.
This task is here mainly to track the prerequisites to activate Geoshapes on production. In this context, activate on production means removing the referer check. Geoshape is already deployed, but its use is limited by a referer check.