Here's how to add/edit/delete appointment categories under the 'Calendar' tab, and in Knowledge Base. These categories are report-able.
First, navigate to 'Calendar' in the main left menu and select 'Appointments/Activities/Reminders'. Next, click on 'Appointment/Activity Types' under 'Tools' in the left menu:
Click on 'Add New' to create a new category type(s). If you need to edit or delete a category, you can select the pencil or trash icons:
Note: If you delete a category type, any appointments made under that category will be deleted also.