Whats the difference between COPD and chronic airway obstruction?

One kind. COPD is one form of chronic airway obstruction. Asthma, chronic bronchitis, obliterative bronchiolitis, small airway disease, bronchiectasis, etc. Etc are other forms.
Difference.... COPD stands for chronic obstructive pulmonary disease. Patients with COPD have chronic airway obstruction. There are other disease which can also result in chronic airway obstruction besides copd; COPD is just one disorder that causes chronic airway obstruction.