They all have many small parts and it is essential that you be familiar with all the parts, how they work, how to take apart, clean and put a brush back together. I cannot stress cleanliness enough. As with an expensive sable brush, the better it is taken care of, the longer it will last. The most important parts of the airbrush are the needle, tip, aircap, trigger, plunger, body, hose, and airsource. People use canned air, CO2 tanks, and motorized compressors to push air through the gun.
Airbrushes also come either single action or double action.
A single action brush has a trigger that when depressed, feeds a specific amount of air and paint through the tip. You cannot control the amount of air but can control the amount of paint, usually by tightening a nozzle on the front of the brush. These brushes are good for mural work or anything not requiring small details. A double action brush allows you to shoot air alone, or air and a controllable amount of paint while you are spraying. They are the most versatile brushes, are ideal for detailed work, and are less frustrating to learn on.