The Kayak app is a travel planning and booking platform that helps people find the best deals for flights, hotels, car rentals, and more. Users can compare prices, sort options based on different criteria, and find flights or hotels quickly and conveniently. To use the Kayak app, download it from your device's app store and create an account. Then, you can search for your desired flight or hotel and compare prices. The process is user-friendly and straightforward.

You cannot book directly on the Kayak app. Instead, Kayak is a travel search engine that helps you compare prices and availability of flights, hotels, and rental cars from different travel websites to help you find the best deals. In other words, it's a meta-search engine — a tool to discover which booking sites have the lowest rates for your desired accommodations or flights. When you're ready to book through one of those sites, Kayak redirects you there so you can complete your purchase on their platform instead.

The Kayak app is free to use. You don't have to pay fees to download or use the app's search engine. You may only have to pay when you purchase a ticket or book a hotel room through Kayak. In that case, the cost will depend on the airline or hotel you choose, not the app itself.