It is the equivalent of touching the hand of your partner or spouse. It is your cat making contact with your through your natural body scent. For your cat it is a confirmation of your presence. Perhaps too it provides your cat with a reassurance that you are you and not someone else. This is an interspecies friendship. We all know by now that cats rely on their sense of smell a lot more than humans. It is like another pair of eyes for a cat.
Cats will also sniff the nose to smell your breath. It is all about the power of body scents – so important for cats.
Whereas a loving husband might touch his wife gently on the shoulder or give her a little kiss as he passes her to reassure her and tell her that he loves her, a cat will smell your face and perhaps follow it up with a lick. Same difference 😉
In answer to the question, it does not mean anything. It is not meant to mean something. This feline behaviour serves a purpose as described.
That is my take on why a cat sniffs your face. I have not read anything on this. I have not checked for any studies because there won’t be any. I have simply thought about it briefly and presented those thoughts here. You may disagree and have a better reason. I’d love to hear it.
Happy Christmas to all visitors. I appreciate your patronage.