index.html - simple page to load Coral UI on a page. (AEM has to be running to delivery the Coral js and css) use this page to try out Coral component:
Reference with sample code for each: https://helpx.adobe.com/experience-manager/6-4/sites/developing/using/reference-materials/coral-ui/coralui3/components.html
shows you how to get WKND source code building and deploying in your local sandbox.
how to debug java code in AEM
HTL REPL samples