Quickstep is an app that is pre-installed on Android devices and is used for app switching and navigation. It is the default launcher for stock Android, which is the default Android experience developed by Google. Quickstep is the entire launcher, including home screens, app drawer, and recent apps, and it does the entire GUI for stock Android. Quickstep allows for quick app switching using gestures, and instead of relying on buttons, you can swipe left or right on the screen to switch between apps in the recent apps list. Quickstep is available on Android devices running Android 9 Pie and newer versions.
It is important to note that there is another app called Quickstep that is not related to Android. This Quickstep is a browser for the physical world that delivers information and apps to users based on the places and things around them. It is used to provide location-based data for retail, hospitality, travel, museums, real estate, and more.
In conclusion, Quickstep is an app that is pre-installed on Android devices and is used for app switching and navigation. It is the default launcher for stock Android and allows for quick app switching using gestures.