Service Territory Location is a junction object that links Service Territory and Location objects[236].
Related Lists are components on page layouts that show records that are related to a record through
a lookup or master-detail relationship[237]. Adding the Service Territory Location Related List on the
Service Territory page layout and adding the Service Territory Location Related List on the Location
page layout would allow Universal Containers to show how Locations are associated to Territories by
displaying a list of Service Territory Locations on each record[238]. Creating the Service Territory
Location as a Service Territory lookup field or creating the Service Territory Location as a Location
lookup field would not work because they are not valid fields on either object. Reference:
https://developer.salesforce.com/docs/atlas.enus.api.meta/api/sforce_api_objects_serviceterritorylocation.htm
https://help.salesforce.com/s/articleView?id=sf.customize_related_lists.htm&type=5
https://help.salesforce.com/s/articleView?id=sf.fs_service_territory_locations_overview.htm&type=
5
