WildStar is employing to check out features that aren't ready for more public consumption, things lacking little bits of polish like "textures" or "fully functional mechanics." It's a group that Carbine Studios freely admits to copying from ArenaNet, and it's also the subject of the most recent WildStar Wednesday penned by community director Troy Hewitt.
Hewitt explains that core testers are meant to be people clearly passionate about the game who are willing to sit through long lists of known issues to test features very early in the development process. The goal is to get outside feedback from an early point to see if some major idea needs a major overhaul now instead of after much of development has been finished. For more information on the testing process and some information about getting noticed by the WildStar team for this elite group, check out the full article.