Each app (created with PowerApps) has an url to run the app in a supported browser. This url can be found found in the “Web link” property in the app “Details”.
When you run an app this way, the navigation bar will be shown by default. An example of this navigation bar is shown below. The app is called “Knowledge Base” in this example.

This navigation bar can be hidden when adding the following to the url:
hidenavbar=true&
right after “app?”. With this, you can make pre-defined links to apps without showing the navigation bar.
This only works for canvas apps!