Online travel agency (OTA)

An online travel agency or OTA is a business that allows users to search and book travel products such as air tickets, lodging, car rentals, tours, cruises, and more. In other words, OTAs are intermediaries between travel inventory suppliers (airlines, hotels, tour operators, etc.) and customers (usually they are travelers or other OTAs).

OTAs often act as tour operators making tour packages and also provide additional travel-related information like reviews, tips, and so on.

OTAs source most of their inventory either directly from end suppliers (via APIs or an extranet) or through such middlemen as GDSs, air consolidators, bed banks, hospitality marketplaces, other OTAs, channel managers, etc. (typically, via API integration). 

On the customer side, OTAs have an online search and booking interface for travelers to make reservations and often a set of APIs for efficient B2B connection with distributors.

The biggest OTAs today are Expedia Group (including Expedia, Vrbo, Travelocity, etc.) and Booking Holdings (including Booking.com, Priceline, Agoda, etc.).