A native app has the same objects as the webapp, but stored on the mobile device itself. When a synchronise event is triggered, any changes to these objects will be sent to the Mendix runtime and stored in the database, from where they can be retrieved and viewed on a webpage.
When a new object is created on a mobile device, it will also become available for a webpage after synchronisation.
So basically, when a user enters data in the native app, another user can view that data on a webpage as soon as the synchronize activity finishes.