This is not as confusing as it seems.
Service types are all the different types of services your business offers. You may have one or several. For example the clinic below offers Osteopathy, Podiatry and Remedial Massage.
You can have a number of appointment types for each service you offer. These can vary in duration and price. You can select an appointment type from the drop down menu in the “Booking” pop up box when a time slot is selected for the desired service.