The dragon runes or the dovahzul are the runes found inside burial grounds. They are the runes that form the dragon language or the dragon shouts. It isn't common knowlegde that dragons speak to each other but it is true. It was magizoologist Gardhun Witlfire that found that the dragons rumble and roar at each other. He called those roars and rumbles shouts or dovahzul. Gardhun wrote down the shouts in ancient runes in a format he believed was understandable for mankind. He had no idea that he invented a new type of rune set. His format was a basis for an advanced language used by a dark society.
It was in 1785 that a group of pure blooded wizards formed a secert society. They called themselves the dovah sonaak or dragon priests. They were 13 wizards that had studid for magizoology and believed in their twisted minds that dragons should rule the world in destruction and fire. These 13 wizards were in the day seen as the first death eaters of sort. They were responsible for the riots in the Netherlands and some murders within pure blooded families inside the wizarding world. The dragon priests believed that "those of pure blood were an ideal sacrifice for the dragons, their lords, and that it could only be a pure sacrifice if they were slain by those of pure blood". Legend claims that if the pure spill the blood of the pure, when brothers kills brothers, the dragons will rise and rule the world. No proof of this legend was ever found but the 13 dragon priests strongly believed in this legend. It was the foundation of their secret society.
In order to communicate within the society the dragon priests studied the formats that Gardhun had made of the rumbles and roars that dragons use to communicate with each other, and based on that format the priests perfected the dragon runes. It was claimed that the dragon priests drank an infusion of wormwood in order to understand the dragons better and to perfect the format Gardhun had made. In current wizard society, we'd call thes 13 priests madmen. It is true that the dragon priests were mad but they left us a great set of magical runes that hold both dangerious and useful magic.
The dragon runes can be used to create traps or dragon shouts whilst in combat. A dragon shout or thu'um is a string of wordless magic that is based on vision and tongue. Vision by imagining the rune inside your head, seeing how it forms and how it works, and tongue by shouting the rune. We'll explain how this works later on under dragon runes in dueling.
In this class we'll discuss the more harmless shouts that can knock back your opponent but seeing the dark nature of the dragon priests, it would be a lie to say that shouts are completely harmless. Shouts are divided into four main categories, being fire, frost, allegiance and disarming. Obviously the fire and frost shouts are very lethal and have been illegal to use within the wizarding world since 1860. We will not discuss the runes or shouts that fall under those categories. We will take a peak at the other two categories as they are very useful in combat.
The dragon priests created and invented the runes or dragon shouts between 1786 and 1810 but their little cult was deemed illegal and shut down by the wizarding world in 1815. This was due to the fact that the dragon priests started to murder pure blooded families. The Ministry of Magic found the 13 wizards and ordered them all to receive the kiss of the dementor. It was said that all 13 also committed a horrible crime by murdering and drinking unicorn blood in order to prolong their lives. It is said that the 13 wizards couldn't be killed and were banished and locked away for eternity. It is claimed that their ghosts still haunt their prisons. Let us take a look at the 13 dragon priests. We have only ever found evidence of their self pronouced dragon names. We have: the leader Hevnoraak, Krosis, Morokai, Nahkriin, Otar the Mad, Raghot, Vokun, Volsung, Miraak, Vahlok the Jailor, Ahzidal, Dukaan and Zahkriisos.
While legend claims that the 13 dragon priests are still "among the living", no proof of this has ever been found. We do however have their legacy - the dragon runes. The dragon runes, shouts or thu'um can be used when dueling. We will discuss how that works now.
Dragon Runes in Dueling
Inorder to use a thu'um we must start by clearing our minds and visualising the runes. In the picture below you will see the dragon alphabet. As mentioned before, the thu'um forms itself by vision and tongue. 
Vision must be used in order to form the runes inside your head, while tongue is used to "speak" the rune. Below you can find the list of thu'ums that are allowed to be used when dueling. You can both use wandless magic or wand magic to create the runes.
Steps to create a thu'um
1* clear your mind.
2* visualize the order of rune words inside your head.
3* shout the rune inside your head.
4* let the magic boil up inside you.
5* release the shout.
If you are holding your wand a gush of air will appear and the rune will be cast from the tip of your wand. Make sure to aim properly and keep in mind that runes can be unpredictable. If you are not holding your wand, the gush of air will come from your mouth and the rune will appear as you breathe out. The last way of casting the runes is the basis for the name dragon shout or thu'um. Dragon shout means: a gush of air spreading by either wand or mouth that makes a bursting shout as it is released.
List of allowed shouts or thu'um ( ame of the shout - rune words - use - category)
Animal allegiance - raan mir tash - lets small animals in the area attack your opponent - allegiance
Aura whisper - Laas yah nir - helps you to detect life nearby - allegiance
Disarm - Zun hall viik - disarms your opponent from his / her wand much like expelliarmus - disarming
Dismay - Faas ru maar - makes your opponent run in fear for 10 minutes - disarming
Spectral clone - Fiik lo Sah - creates a ghoslty form of the caster to confuse opponents - allegiance
Unrelenting force - Fus ro dah - makes your opponent stagger, throws his / her back a little - disarming
Whirlwind sprint - Wuld nah kest - makes you run and move faster - allegiance
That concludes it for this lesson. You may now complete your assignment.
referece
Dragon language - wiki
Skyrim the video game
elder scrolls wiki
dragon shouts wiki