Dracomancers can communicate fluently with Dragons. Normal humans, elves, and other people that try to communicate with Dragons always fail, unless the Dragon wants them to speak. But Dracomancers could speak with Dragons whether the Dragon liked it or not.
The most important ability of a Dracomancer is the fact that they could bond with a Dragon easier. Most Dragons do not allow people to touch, ride, or do anything else with a person, unless they are a Dracomancer. Dragons like Dracomancers because Dracomancers know how to treat a Dragon with gentleness and respect. However, some Dragons do bond with normal people. This is rare, though.
In emergencies, Dracomancers could take complete control of weaker dragons and bind them temporarily to their will. However, if the Dragon had not understood why this was necessary, it would then turn on them.