Material Design Lite a library of components & templates in vanilla CSS, HTML and JS.
Google’s Material Design language focuses on simplicity in design and use of bold colors and Typography. With Material Design guidelines, Google aims to establish a unified experience across its platforms and wide variety of devices.
View the detailed information and documentation regarding Material Design at its official website which provides guidelines on design and interaction fundamentals such as animation, color, typography, layout principles and structure, components and essential patterns.
Material design enables app developers to switch android app themes to the new Material Theme along with new widgets and animations. Check this link for details.
Have a look at the Material Design Introductory video below which illustrates how Google’s own android apps adapt with this new design guideline. Also take a look at UI Color Palette and Components