Organization represents a group of people with responsibility. Location represents a physical structure. HealthcareService represents an organization’s abilities (and availability) to deliver a specific set of services at a physical location. For a clinic, you’d typically have both an Organization (who works there and has responsibility for the care delivered there) and a Location (the physical building or portion thereof the clinic operates in) as well as one or more HealthcareServices that describe what’s available when. (E.g. the clinic is available for walk-in medical care from 9-6pm weekdays and 10-4pm weekends, but diabetic services are only available on Tue/Thur and dietary services are only available on Tue and Fri from 10-2.)
Organization hierarchy represents responsibility. E.g. Department 123 is part of Good Health Clinic #57 is part of the Good Health Clinic organization, which is a subsidiary of Megacorp A
Location hierarchy represents physical containment (Campus A contains Building 1 which contains Floor B which contains Wing 2, which contains Room C, which contains Bed 3
HealthcareService doesn’t have hierarchy. Instead it binds together an Organization and a Location and declares what’s available when.
(Location also has hours contact information, but that indicates when the physical doors are open and how to reach the site as a whole - if the clinic is in a mall, the Location availability is going to be when you can get into the mall, not necessarily when the clinic’s services are available.)