VisualVM is just an application which has a predefined and limited set of features. It is a framework, which means that it is possible to extend it. The way in which VisualVM provides for extension is via the plugin API which allows us to create new plugins which are then available through the application. Such plugins can do various things, but are mostly used to provide new ways of monitoring or controlling the JVM applications.
The current (at the time of writing) trunk version of VisualVM requires the NetBeans platform and IDE v.8. So we need to ensure that the current version of the platform is available on the machine. If there is any doubt, check the page with VisualVM trunk build instructions at http://visualvm.java.net/build/build.html.