I have reactive airway disease and not asthma. what is the difference?

Very mild asthma: More and more we are shying away from using that term. It is usually used to label very mild asthma that flares up very infrequently, usually due to a well-defined trigger like infections, wheather change, pollen, etc. There's a reason asthma meds like albuterol are used for this.

May be the same: Reactive airway disease is a more general term that includes asthma, but also other conditions that can present with wheezing or shortness of breath. In older children and adults, reactive airway disease is usually asthma.