The difference between appointments and funnels can sometimes be confusing.
An appointment can be used for any purpose - meeting with leads, having goal setting sessions with existing clients, or meeting a former client for coffee (for example).
A funnel is used specifically to gather new leads, and will automatically enroll contacts into the New Lead Campaign. A funnel will get an appointment type assigned to it, as it'll provide a call-to-action for all contacts to book the appointment.
The video in this lesson dives into this topic a little deeper.