To eradicate confusion:
PEX: Essential private Minecraft server administrator commands (PermissionsEx)
'group set': command to set players in a permission group created in the PEX main text file
Sorry to inform you, but Evan was sniping at the exclusivity of "only x will get this," which particularly in this case is not only not exclusive (because it's very easy to understand what's going on with very little foreknowledge), but is also just asinine in general. "Only x will get this" is like the oldest form of clickbait, it's there for either furious circlejerking or provoking an indignant response. Both of those things generate views and interest, which is why it's such a classic clickbait tactic. As seen here, though, it can also be used to just be an elitist douche without trying to get pageviews.