Filters allow you to clarify the display and your booking's list, on reservations note-book's side or on room plan. A filter with a "grey" color (as here the last one) means that it is activated.
Here are their meanings :
1: Booking to be validated 
2: Booking validated / confirmed without tables' number
3: Booking validated / confirmed with tables' number
4: Booking honored / awaiting other dinner's guests / partially honored
5: Booking cancelled and no show