[link|http://en.wikipedia.org/wiki/Tuberculosis#Transmission|Tuberculosis] is transmitted via an airborne vector. That means when someone with active TB coughs, sneezes, spits, kisses you, or [b]talks[/b] near you, they're releasing TB bacteria into your local airspace.
[link|http://en.wikipedia.org/wiki/AIDS#Transmission_and_prevention|AIDS] is not transmitted in the same manner, instead generally requiring sexual contact or usage of the same needle as an infected person.