PerformerJS allows you to add really cool effects and features to your website by doing some simple editing of the HTML code in your pages.
I think that Performer has the potential to make life much easier for website developers who want to get the basics done quickly. A lot of those developers use WordPress to create sites, so a simple plugin was a no-brainer.
For example, for every 'toggler' link on the page Performer will attach a click listener to the link so then it is clicked the visibility of the target element is toggled. Simples.
There's loads more information in the Documentation.