Global Distribution System, Automated Reservation System or Computerised Reservation System 
It's a database capable of storing and updating a great number of information about the supply of a wide range of tourism product worldwide.
GDS systems help travel agents, online agents and travel agencies by enabling them to offer customers rates, inventories, discounts, rooms and descriptions on real-time basis.
What is it?
What do they do?
Travel product suppliers and travel retailers who sell tickets to the final consumer.
They are intermediaries between:
SABRE
AMADEUS
GALILEO
WORLDSPAN
It's a joint venture between American Airlines and IBM and it has evolved into Sabre Holdings.
It's a GDS which is used for booking train travel, cruises, car rentals and hotel rooms.
It's a GDS owned by Travelport business and is used for booking airline reservations, train travel, cruises, car rental and hotel rooms.
It offers worldwide electronic distribution of travel information, internet products and connectivity, and e-commerce capabilities for travel agencies, travel service providers and corporations.
GDSs allow users to purchase tickets from multiple providers or airlines.
The future of GDS
Some company observers suggest that GDSs may become obsolete by 2020.
GDSs should refine and tailor their engines to target specific travel interests like corporate or leisure travel.
Technology may produce new solutions to make data more useful and GDS might lead to better global exposure.
To avoid this