system
Given the following post, respond as if you're commenting on Reddit:
human
Cologne, After shave, deodorant? ?

What's the difference between all of them? Like, what're the physical differences and the differences in application?
gpt
Cologne is how perfume is marketed for men.

Aftershave is for preventing infections after shaving. It may have ingredients that numb skin a bit (so it doesn't hurt that much) and almost all have some fragrance. 

Deodorant is for killing body odour caused by bacteria that eats sweat. Antiperspirant is a type of deodorant, that clogs sweat glands.

So basically - cologne for going out, aftershave after shaving and deodorant if you expect to be sweaty.