Material Design is the look and feel of the next Android version, L . Or whatever Google wants to call it. The new look and feel is suppose to be flatter and makes more uses of cards (PalmOS?) . To communicate the message, there is a website on what to do and not do.
Everytime Google rolls out an improved UI, I cannot help hearing sniggers going on in Apple. After all they re-wrote the hand book on smartphone UI.
Have a read yourself. link