Booking in advance refers to reserving a hotel room, restaurant table, or space in the banquet hall for a specified time in the future through a mutual agreement between the guest and hotel. Advance bookings can be made verbally over the telephone or through written communications like mail, fax, email, or third-party reservation systems. Reservations come from various sources like individual travelers, companies, airlines, governments, or non-governmental organizations reserving rooms for their purposes. Reservations can be tentative if a guest is unsure of their plans or confirmed when agreed upon in writing by both the guest and hotel.