Set this attribute to true to add padding when your app is running on earlier Android versions (API level 20 and earlier). This setting prevents CardView content from intersecting with the CardView's rounded corners.
Set this attribute to true to add padding when your app is running in versions of Android at or greater than API level 21. If you want to use CardView on pre-Lollipop devices and have it look the same on Lollipop (or later), set this attribute to true. When this attribute is enabled, CardView adds additional padding to draw shadows when it runs on pre-Lollipop devices. This helps to overcome the differences in padding that are introduced when pre-Lollipop programmatic shadow implementations are in effect.