It opens from a link, stays on your home screen if you want, and updates itself. No store, no waiting.
Storage used
It doesn't fill up your phone's memory: what's needed loads only when it's needed.
New features available from the very first launch, with no store involved.
Push notifications, full screen, a home screen icon: the experience is just like a native app.
Open the app: it will guide you through the install on your phone, step by step.
