When you pin a screen on Android, it keeps the screen open on top of everything else on your phone and deactivates the phone’s buttons. You can even activate a setting to require the unlock pattern to unpin. This is handy to limit access to other data and apps on your phone if you borrow it to someone. This can also be good if you’re letting a child use your Android device and want them to stay in one app.
How to Pin a Screen on Android
The instructions may be slightly different depending on your version of Android. I’m running Android 8.1 Oreo on an Essential phone.
Step 1: Turn on pinning in Settings -> Security & Location -> Screen Pinning
Step 2: Pin an app from Overview.
See all the steps in the video below: