Owned by Sabre corporation, Sabre GDS is among the top three global distribution in the world. It's used by travel agents and companies around the world to search & book on one end and it aggregates the worldwide travel contents of airlines, hotels, cars, tails etc on the other side.
New Distribution Capability - IATA NDC is a travel & hospitality industry-supported program launched by IATA for the development, growth and adoption of new XML-based data transmission standard, which is called NDC standards today. This was started in 2012 by IATA to replace the old EDIFACT, which global distribution systems rely on. EDIFACT can only display information such as fares and schedules and need an upgrade to meet the new global standards.
More likely, a central reservation system is used by entities like a hotel or chain of hotels. CRS allows you to manage the inventory and reservations can be done by end customers online or through the front desk. Sabre GDS - global distribution system aggregates and distributes the travel contents (airlines, hotels, rails, rentals) through a single seamless interface.