Global Distribution Systems (GDS) are worldwide reservation systems that allow travel agents, websites, and companies to book flights, hotels, rental cars, and other travel services through a single access point. Property information like rates and availability are loaded into the GDS networks and then retrieved by online travel sites and agents. The four main GDS are Galileo, Worldspan, Sabre, and Amadeus. Integrating with a GDS expands a property's distribution by making their inventory accessible to the large network of travel sellers connected to that system. This provides benefits like 24/7 connectivity, greater market reach, and coverage through agent programs.