Official Description: The Support Library is a static library that you can add to your Android application in order to use APIs that are either not available for older platform versions or utility APIs that aren't a part of the framework APIs. Compatible on devices running API 14 or later.

CommonsWare’s Notes

CoordinatorLayout is designed to help coordination among widgets for runtime events.

The classic example is showing a Snackbar or similar sort of content at the bottom of the screen. It may be fine that the Snackbar overlaps some of your widgets, but other widgets you might prefer “move out of the way” while the Snackbar is on the screen. For example, you might want to move a FAB such that the Snackbar does not overlap it.

Otherwise, CoordinatorLayout behaves much like FrameLayout. You tend to use it in conjunction with something else, such as a ConstraintLayout, for the actual “layout” of the widgets in terms of sizing and positioning.

In practice, many developers use a CoordinatorLayout when documentation for some library suggests to use it. If neither you nor library-supplied widgets are doing anything special to take advantage of CoordinatorLayout capabilites, it does nothing for you on its own.

Note that CoordinatorLayout originated with the Design Support Library. Many articles from 2017 and earlier will reference Much of what was written for that CoordinatorLayout should still be relevant for the AndroidX edition.