This application works directly inside Etsy, because really, what's the point of applications that are in third party websites?
Enhantsy works by tightly integrating with etsy.com making enhancements and features requested by the Etsy community but not implemented by Etsy. Some enhancements are re-introducing functionality once present at etsy.com and since removed. Others are new ideas not (yet) implemented on etsy.com.
Enhantsy sits at the top of your etsy.com pages and quietly rewrites them with new functionality. Once installed an Enhantsy link is displayed in the links across the top of the page. Clicking this opens a menu allowing you to toggle which enhancements are enabled and gives links to specific Enhantsy pages.