Widevine DRM is a Digital Rights Management component. A device requires hardware-backed DRM measures to process protected media content. For a device to display HD videos from a Widevine-backed service, it must be L1 certified. L3 certified devices can only display SD videos regardless of the subscription plan or device capabilities.
This app shows you the security certification level of your device. The security level also decides the streaming quality supported by a streaming app such as Netflix, Amazon Prime and Youtube.