Mobile application development can be expensive and time-consuming, involving multiple ecosystems running on diverse devices which have to conform to different standards.
Web Apps are browser-based applications, built to offer similar levels of functionality to native mobile apps. They can run on multiple device formats without the need or expense of designing and building different versions. Using mobile-responsive design, Web Apps will run on desktop and laptop computers, reformat for tablet devices and scale down to mobile phones.
Progressive Web Apps (PWAs) are rather like Web Apps on steroids, which function and feel much more like conventional native apps. They can be downloaded and installed on your mobile device and they launch in a standalone window, just like native apps. They're responsive to any screen size, they can provide offline functionality, and they can be searched for on your device. In short, although they're technically "just" websites, they can offer so much more.