The Android Support Library is not actually a single library, but rather a collection of libraries that can roughly be divided into two groups: compatibility and component libraries. For details, please see Understanding the Android Support Library.

support newer Android features on older Android versions.

library to reduce the number of nested views needed.

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.

perform actions in response to a change in the lifecycle status of another component, such as activities and fragments.

library to help with material design guidelines.

library to help with material design guidelines.

library to help with material design guidelines.