Polymer is a lightweight library that helps you take full advantage of Web Components.
With Web Components, you can create reusable custom elements that interoperate seamlessly with the browser’s built-in elements, or break your app up into right-sized components, making your code cleaner and less expensive to maintain.
In fact, Polymer's task is not only to simplify the creation of sites, Polymer should help create web applications that can function without additional interference on various devices: from desktops and mobile platforms to TVs. Polymer can be called the embodiment of Material Design for the web.
Polymer went from an experiment to a Big Thing serving tons of users in major Google products and some of the biggest companies in the world in no time. Success is great! But there’s always room for improvement. Mistakes were made. Lessons were learned. Regrets were had. Two years, hundreds of elements, and thousands of apps later, we’ve got a pretty good idea what makes an element and an app great, and what’s changing in Polymer 2.0 as a result.