What's the difference between COPD and Emphysema?

Emphysema is a specific lung disease and COPD (chronic obstructive pulmonary disease) has many causes, like emphysema, and mesothelioma, to name two. They will most likely be on O2 the rest of their lives, but maybe not.  They can get a portable tank and still live active lives. My dad is not on O2 yet (his pride!) but has been diagnosed with emphysema and COPD for 15 years,,,yes, 15 years. I never thought it possible. Until recently he pretty much did what he wanted, but it is hard for him to travel now..otherwise, he wood carves, and plays poker, and used the internet and his Kindle and is enjoying a great quality of life, even with his problems (he also has severe heart disease but is alive at 75!!!!!).  He does not smoke anymore, and follows a ll his MDs orders, bless his heart...including being basically a guinea pig for all the new meds. And he is on a great cardiac exercise program, 3 times a week , at a local hospital.