The main difference is in the droplet size and airborne and droplet have different precautions.
I would go to the CDC site. I found great info on it before my NCLEX exam--and I did have questions pertaining to different precaution measures on the boards.
TB is considered airborne, along with measles, and varicella. You need a specific mask when in with the patient (N5). The room is also a negative pressure room.....etc.
With droplet (pneumonia, etc.) you must wear mask within 3 feet of patient.
The list is quite long with droplet infections, so if you at least memorize/learn what is considered airborne, it makes it easier.
The CDC is great--it precisely defines all precautions and what measures to take--you will find what you need there--with better explanations