Progressive Web Apps (PWAs) are designed to give users a native app-like experience through features like push notifications, offline access, and load quickly while using modern web technologies. PWAs leverage tools like manifest files, service workers, and push notifications to make web apps more engaging, fresh, fast and installable on home screens. Requirements for developing PWAs include using the latest version of Chrome, HTTPS, a local server, and HTML/CSS/JavaScript. Many large companies like Pinterest, Trivago, and Twitter have adopted PWAs to improve user experience on their mobile websites.