Natours is a web application that allows admins, tour guides, and lead guides to post tours, and for people to buy them. The application is built using Node.js and Express.js on the backend, with a MongoDB database, and Pug as the templating engine for the frontend. Users can browse available tours, search and filter them by location, price, and other criteria, and make a booking by selecting a tour and choosing the desired date and number of people. The application also allows users to create an account, save their favorite tours, and manage their bookings.