Apps on HoloLens use either 2D view or holographic view. Apps with 2D view look like windows, and apps with holographic view surround you and become the only app you see.
To run apps, first you need to place them in your world. HoloLens will remember where you've placed your apps.
Open and place apps
You'll find your apps either pinned to Start or in the All apps list. To get to the All apps list, bloom to go to Start, then tap the plus sign Add.
On Start or in the All apps list, select an app.
Use your gaze to position the app where you want it.
Air tap to place the app, or say "Place." The app will then be active.
Up to three 2D app windows can be active at a time. You can open more, but only three will remain active.
Each open app can have one active window at a time, except Microsoft Edge, which can have up to three.
If you're having problems placing apps, make sure there's enough light in your space, and walk around so HoloLens has a current scan. If you keep having trouble, see HoloLens and holograms: FAQ for more info.
To close an app that uses 2D view, gaze at it, then select Remove
To close an app that uses holographic view, bloom to leave holographic view, then select Remove