In keeping with the philosophy of the re-use of code, Polymer is a web development framework in the encapsulated - operation and interoperability of custom elements that extend the HTML. The Web Components It is built with Polymer, they end up being HTML tags individuals that encapsulate operation and which may or not have attributes that allow interoperability with the same.
This project from Google brings the Material Design to HTML5 applications 5, and in this way he intends to improve the user experience in this type of apps whose use is in constant growth.