Overdraw
An app may draw the same pixel more than once within a single frame, an event called overdraw. Overdraw is usually unnecessary, and best eliminated. It manifests itself as a performance problem by wasting GPU time to render pixels that don’t contribute to what the user sees on the screen.
Links
https://developer.android.com/topic/performance/rendering/overdraw
https://medium.com/wenable/overdraw-in-android-b3ecaaa620b5