Dawn communicates via Mavlink protocol with flight controllers. Dawn can be configured to output either position setpoints or velocity ones, though the default of velocity based setpoints is recommended for smoothness.
Depending on how Dawn is configured by the APP being run, Dawn will either handle the entire mission (in the case of subject tracking for example) or only take over for collision avoidance. For example, Dawn's inspection App, which is provided for free, works with mission files output by ground control software like Mission Planner, and tries to fly as closely to the desired path as possible, deviating only when necessary due to obstacles or aircraft.
Dawn will pull the craft velocity, position, acceleration and other properties from the flight controller via Mavlink. These properties are used by Dawn internally.