Faaz! Paak! Dinok!

A battlecry, spoken through barely functional vocal cords and with an old curved blade being wielded, too ancient and too long since the blood of its foes dripped from the edges.

You've heard it before, haven't you? The words are always raspy, always thrown in during the heat of battle, before their creaky bones and the rotting remains of their flesh collapse in heaps, their iron armor stuck to them permanently.

Cursed, they are, perhaps?

A theory. One of many, only known and heard among the few that have wandered into the ancient Nordic tombs and have lived to tell the tale.

Why do they walk, after all these years? Why do they still wield their battleaxes and their swords? Why do they not rest?

Another theory is that this was a punishment from one of the divines, from not being appropriately worshipped, or perhaps because they weren't put to rest as they should've been, left to rot wrongly with their souls still stuck in their bodies.

Ah. There it is.

Its cause is unknown, and who is the culprit behind these cursed beings is, too, unknown, but one thing we are aware of through practice and observation are the souls.

Trapping their souls, then struck, and allowing it to flee in a gem, we can see that they do have souls.

This is strange, considering that dead things do not have souls, as they do not remain in the bodies when they die.

What is keeping their souls in place? Why aren't they going to Sovngarde?

Ah, but Draugr, although classified as dead, aren't truly "dead." They contain their souls and a whisper of life.

Interestingly enough, they are additionally classified as "barely living" men, which is a fascinating way to word things, as it implies that Draugr are people, who are barely alive.

Of course, that should be impossible - they are nothing but bones and ancient rotting flesh. There is only so on-the-edge one could get to death before they go teetering off into lifelessness, but Draugr seem to go beyond that.

Due to their almost-but-holding-on lifeless forms, I conclude that Draugr are a kind of immortal beings.

This, actually, may be the differences between skeletons and Draugr, aside from their noticeable gap in strength. While walking and attacking skeletons are produced from Necromancy, Draugrs are those cursed with immortality, a kind of immortality that does not allow themselves to entirely rest in death, instead, slowly rot away but still forced to be alive (It is important to note that immortality does not refer to invincibility, the inability to die or be killed. The definition of immortality is "the ability to live forever." Unlike most humans, theoretical immortal individuals would not have an "expiration date," and cannot die from natural causes, but others can force the end of their life through murder).

But why do Draugr still hold onto their souls? Why do they contain a whisper of life? Why are not truly dead? Why were they cursed with this immortality?

Well, the answer to all these questions are unknown, but there are various theories to go around, and we will look at them.

The first theory is that Draugr are immortal servants, bound to dragon priests or other such powerful individuals and serve them, even in almost-death. This theory likely originated due to the amount of Draugr that are near places of Dragon Priests, protecting them and working with them to attack those who disturb them. However, due to the number of sites that are not related to dragon priests and do not contain such a being, this theory might not be entirely accurate, although it does make some interesting and useful points.

The second theory is that Draugrs are the result of men who performed acts of cannibalism after being trapped on Solstheim, who were then cursed by the "All-Maker," a deity of the Skaal said to have created everything, because of their vile deeds.

The third is that the dragons had cursed them for their acts of betrayal and revolution in the Dragon War, giving them their horrible never-resting immortality... which makes sense, and would explain the flaws in the first theory.

The battlecry, "Faaz! Paak! Dinok!" is in Dovahzul, the dragon language, as well as all of their other dialogue. They speak in the dragon language, while their tombs usually have a word wall in it. Additionally, sometimes, Draugr could be left to Dragon Priests as immortal servants, bound forever.

An additional few things to note is that Draugr seem at least mildly intelligent - they can speak a language, and according to a book in Skyrim, Amongst the Draugr by Bernadette Bantien, they seem to be able to communicate with one another. 

They also seem to be able to worship and hold religious practices.

In conclusion?

Draugr are people of Atmoran and Nordic origins who were cursed in the Dragon War for their betrayal, living as immortal servants until somebody puts them to their final death.

Draugr are immortal people. People. They aren't even skeletons, and although they are classified as undead, they aren't undead. They're living immortals who probably suffered from starvation and disease, and that's why they look the way they do.

They sound so horrible because they don't have very much water and their vocal cords are torn and not functioning correctly, and they're speaking in a dragon language.

You're not killing undead. You're killing actual people that look unhealthily bad.