Material Design

Material Design (codenamed Quantum Paper) is a design language developed in 2014 by Google. Expanding upon the "card" motifs that debuted in Google Now, Material Design makes more liberal use of grid-based layouts, responsive animations and transitions, padding, and depth effects such as lighting and shadows.

Google announced Material Design on June 25, 2014, at the 2014 Google I/O conference.

Designer Matías Duarte explained that, "unlike real paper, our digital material can expand and reform intelligently. Material has physical surfaces and edges. Seams and shadows provide meaning about what you can touch." Google states that their new design language is based on paper and ink.

Material Design can be used in API Level 21 (Android 5.0) and newer or via the v7 appcompat library, which is used on virtually all Android devices manufactured after 2009. Material Design will gradually be extended throughout Google's array of web and mobile products, providing a consistent experience across all platforms and applications. Google has also released application programming interfaces (APIs) for third-party developers to incorporate the design language into their applications.

As of 2015^[update] most of Google's mobile applications for Android had applied the new design language, including Gmail, YouTube, Google Drive, Google Docs, Sheets and Slides, Google Maps, Inbox, all of the Google Play-branded applications, and to a smaller extent the Chrome browser and Google Keep. The desktop web-interfaces of Google Drive, Docs, Sheets, Slides and Inbox have incorporated it as well.

The canonical implementation of Material Design for web application user interfaces is called Polymer. It consists of the Polymer library, a shim that provides a Web Components API for browsers that do not implement the standard natively, and an elements catalog, including the "paper elements collection" that features visual elements of the Material Design.

...
Wikipedia