OTA stands for Online Travel Agent and acts as a 24/7 sales representative for hotels, providing a one stop solution for hotel bookings. There are two main OTA models: the Merchant Model and the Agency Model. The Merchant Model involves contracts where OTAs purchase rooms in bulk from hotels at discounted rates, typically earning 20-30% margins, whereas the Agency Model uses commissions per room sold and allows hotels to set the final price. The Merchant Model provides OTAs with better deals but may be less preferred by hotels, while the Agency Model requires no upfront costs but offers OTAs less bargaining power and profit margins.