The snippet manager is a python panel that features a lot of collected vex snippets and allows you to store your own.
It also gives you an overview of all the vex includes, vex custom variables as well as www links to specific curated content such as the master classes.
https://vimeo.com/showcase/5860456/video/363448342
Links category of curated Links of Master Classes and other Content
https://vimeo.com/showcase/5860456/video/523941550
Easy way to browse functions within the various vex include files that ship with Houdini.