As cool as the Battle of Winterfell was, Game of Thrones left us with a lot of lingering questions about the Night King and his army. Chief among them is, who are his commanders? The mysterious undead leaders of the Night King's army are White Walkers, seemingly capable of plotting complex military maneuvers without ever uttering a word. You can tell the commanders from the wights, because like their leader, they look almost human. They're not decaying or wearing rags; instead, they're outfitted for battle and even ride horses on occasion. They can also create wights, which helps keep their army full of new recruits.
Sadly, the show never goes into the particulars of why the White Walker generals are so different from the wights, but we can make a guess. In season two, we see that Craster, Gilly's father (and husband) who is also an ally of the Night's Watch, sacrifices his baby sons to the White Walkers. In season four we get a little more insight about what happens to the babies. The White Walkers turn them into creatures with icy blues like their own, but since they're not dead when the change occurs, it's possible that they grow to become White Walkers, rather than the more mindless foot soldiers that are the wights.
This is never confirmed on the show or in the books, but it would explain why the commanders are more human than the wights. It would also go a long way toward explaining why they can bring wights to life, just as the Night King can. Basically, it's like an undead pyramid scheme. The Night King makes the White Walkers who serve him and possess the same kind of magic that allows them to make wights, too. If you kill one of the commanders, then all of the wights that the commander ever made will fall. And as Arya demonstrates with her badassery in "The Long Night," if you kill the Night King, it wipes out not only the wights, but also the White Walkers.
Unless something unexpected happens in the final episodes, it seems this chapter of the show's mythology is closed. That means a definitive answer about the nature of the Night King's White Walkers may never be given (unless the potential prequel series decides to tackle the White Walkers' origin story in depth). Until then, fans will have to speculate about this particular Game of Thrones mystery.