A Web App is simply a website optimised for mobile devices (phones/tablets) that look like a mobile Native App. They use a Responsive Layout for providing an optimal experience for all mobile devices and orientations (landscape/portrait). A Responsive Layout = Fluid Layout (width %) + Flexible Image (width %) + Adaptive Layout (Breakpoints). I created many Web Apps for the event industry when I was working in Crystal Interactive but I cannot show them here due to copyrights. Here some examples of prototypes.