<link rel="import">).
<polymer-element>on-event attributes.
id on this.$, eliminating
boilerplate querySelector's.
Ready to dive deeper? In this tutorial, you'll build a small Polymer application -- a very basic client for a social networking service like the one at right. It'll give you a good feel for both using pre-made Polymer elements as well as building custom elements of your own.
If you'd rather keep reading, head to the Polymer docs page to dive deeper.