I by no means object to Jmat's answer--it's a correct answer, definitely. Just to address the rest of your question though--here's how I'd reword what you had written: "What should I call the hair which grows on the human body, e.g. on the chest or in the armpits? Is everything named hair or can I call this fur? I was told that fur as a noun is supposed to refer to the hair of animals. Please let me find out more about it. Please correct my questions as well which I have written." To address more on the topic though, it is odd that one word can mean either plural or singular, based on context. "He combed his hair" refers to plural (like an aggregate noun), more than one strand of hair, while "A hair grew on his earlobe" would be singular (distinguished by the indefinite article "a"). We do need to see "a" or "the" or "a strand of" to see it as singular. And yet, there is "hairs" which could refer to more than one type of hair, like blond, brunette, etc.

Any hair that isn't on your head is called "body hair". You could also be more specific ex. arm hair, chest hair, leg hair, arm hair, armpit hair etc. Fur is only used to describe hair on non-human animals.

everything _is_ named hair human -- hair animal -- fur