Everyone stops smoking eventually
The trick is to stop while you are still alive (and preferably while you have some lung function left)
Here's the wiki page
The British Thoracic Society has a pamphlet thing you can download and it's pretty easy to understand and the Arizona Respiratory Centre has a good site.
Emphysema is a disease of the lungs
It is most commonly caused by smoking but there are some other minor causes which contribute such as alpha-1-antitrypsin deficiency, but these are rare. Smoking is by far and away the biggest cause of emphysema.
It occurs in the aging population much more so than in the young but this tends to depend on the amount of smoking and the age it was started. The more you smoke, the younger you are when the emphysema hits.
The lung tissue is destroyed - the normally elastic walls of the alveoli (little balloons of air to get oxygen into the blood) become more rigid and it is harder to get the stale air out so you can't get fresh air in.
Most emphysema patients therefore suffer from Shortness Of Breath and they have to puff and puff (hyperventilate) to get their breath when they exert themselves.
They can sometimes feel as if their chest is tight or even complain of pains (rarely).
The usual tests for emphysema are:
tests for oxygen extraction - the fingertip oxygen saturation probe and the arterial blood gas test
chest x-ray to make sure there isn't any other thing like a pneumonia or pneumothorax (both of which are more common in patients with emphysema) and to rule out cardiac failure
sometimes blood tests to look at a white cell count (looking for pneumonia again)
There are things that can be like emphysema: asthma, bronchitis (both of these are closely related and smoking related illnesses), but then you can have cardiac failure (water on the lung), pulmonary embolus ... anxiety (this is a tricky one as many emphysematous patients develop anxiety disorders)
Treatment is by inhaled medications - ventolin (salbutamol) and other bronchodilators, steroids (budesonide, fluticasone, etc)
and by oral medications - sometimes oral steroids, antibiotics if there is an infection. In the past, theophylline was used.
I hope that all helps.