A CRS typically provides the following functions
Flight schedule information: Days and times for flights operated by the airline
Availability information: Seat availability on a flight by service class, i.e. Economy, Business or First class
Fare quotes: A consolidated fare for an itinerary based on flight, day, time, service class and passenger types chosen
Reservation information: Seat bookings
Ticketing information: Generating and storing tickets
Refunds and cancellations: Cancellation of existing reservations and tickets