'Appointments' and 'Bookings' sound like they could be the same thing, but there's an important difference for reporting purposes.
Appointments are what are on the books for the time period you're reporting on. So if an appointment was booked three weeks ago for this week, it will be counted as an 'appointment' in the 'This week' time bucket (and will be counted as a 'booking' in the bucket three weeks ago).
Bookings track when appointments are booked, whether by the client or by staff. So if an appointment is booked today for three weeks from now, it will be counted as a 'booking' in the 'This week' time bucket (and will be counted as an 'Appointment' in the bucket three weeks from now). If an appointment is rescheduled, the original booking date will be used to determine its 'booking' time period.