A Progressive Web App (PWA) is a type of application software that is delivered through the web and built using common web technologies such as HTML, CSS, JavaScript, and WebAssembly. It is designed to work on any platform with a modern web browser and can operate both as a web page and mobile app on any device. PWAs are built to take advantage of native mobile device features, without requiring the end user to visit an app store, make a purchase, and download software locally. They can be located with a search engine query and accessed immediately through a browser.

PWAs have three pillars that transform them into an experience that feels like a platform-specific application: capable, reliable, and installable. They are responsive and work with many different screen sizes, can run on multiple platforms and any device with a modern web browser, function just like normal native apps, and the updates are independent.

PWAs use standards-based technologies and run in a container that is secure and accessible to anyone on the web. They can send web push notifications, work offline, and be accessible from the home screen, just like a mobile app from an app store.

To develop a PWA, you need to provide a secure server with an HTTPS connection to protect user data and build an extra layer of security within your website. Service workers are a key component of PWAs. They are JavaScript files that run in the background, enabling offline functionality, push notifications, and caching.

In summary, a PWA is a web application that provides a user experience like that of a platform-specific app. It is designed to work on any platform with a modern web browser and can operate both as a web page and mobile app on any device. PWAs are built to take advantage of native mobile device features, without requiring the end user to visit an app store, make a purchase, and download software locally. They use standards-based technologies and run in a container that is secure and accessible to anyone on the web.