ELI5 Air Conditioning - How does it work?

How does AC and refrigeration in general work? Why is Freon gas used? Why do some people say that air conditioning is a cause of Legionnaires' disease?   ... We explain like i'm five!   Thank you to the r/explainlikeimfive community, and specifically the following reddit users whose questions and responses formed the basis of this conversation: theod4re, burried_treasure, off2seethewiz, jbota, futurol & super_ag   To the ELI5 community that has supported us so far, thanks for all your feedback and comments. Send us an e-mail: [email protected]