What is the difference between a mobile app and a mobile website?

A mobile website has to be found again every visit. An app sits on the home screen and can send a notification. That is the whole difference that matters commercially — everything else is a detail.

A mobile site reaches everybody and converts worse. An app reaches only the people who installed it and converts far better. They are not competitors; the app is where your existing customers go.

This is why an app is a retention tool rather than an acquisition one, and why launching one before you have customers to retain is the wrong order.