A travel booking website is an online platform, where end users and agents can search for deals across multiple GDS / suppliers / aggregators and shows you the results in one place. For example, if you are looking for a flight from Boston, USA to Bangalore India - you will find out many options with several airlines to select the specific class at cheapest pricing.
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. GDS - global distribution system aggregates and distributes the travel contents (airlines, hotels, rails, rentals) through a single seamless interface.