Material Design look across Android OS versions, particularly to versions older than Android 5.0.
While there are dozens of classes in this artifact, the only one that you will work with directly (usually) is
AppCompatActivity. If you have your activity inherit from
AppCompatActivity, you are requesting to use AppCompat and to adopt the Material Design look.
If you inherit from
AppCompatActivity, you also need to:
Have a theme that extends from
Theme.AppCompat (or a sub-theme)
app: namespaced attributes for some things in menu and layout resources