We have different types of nouns in English.
When we talk or write, we talk or write about someone or something. If so, then we need to give a name to that someone or something. We cannot avoid names; so we cannot avoid nouns.
In real life we use different kinds of names. In grammar, different types of nouns represent different kinds of names.
It is not immediately clear to many people what grammar means by different kinds of names.
Let's imagine a real life example!
If you were Albert Einstein. People would call you different things: Albert, Mr. Einstein, or even Al or Albie. Your close friends might even call you Mr. Intelligent or Mr. Genius, either to praise you or to make fun of you! If you happened to be in my country, we would address you as Einsteinji or Einstein Sahab or Albertji or even Albert Sir ji!
All these names of Einstein (i.e. you) are different names. We refer to them as names, surnames or nicknames.
However, the different types of nouns in grammar are not about names, surnames and nicknames. Grammar does not treat them as belonging to different types. All of them belong to one and the same type in grammar. They are all called Proper Nouns.
Let's take an example.
Suppose a man comes to meet me at home while I am in my study. My wife receives him at the door and reports to me, "A man has come to see you." She refers to him as a man.
Now suppose both she and I know that he is Joseph, my student. In that case, she would tell me, "Joseph wants to meet you." She would refer to him as Joseph. These two words, man and Joseph, are different names used for the same person...but see how. They are NOT nicknames, surnames, etc.
When my wife said man, I had a vague idea that the person waiting for me was a grown-up male human being and not a woman or child. The information was helpful...somewhat. But, when she said Joseph, I knew exactly who was waiting for me.
A difference of this kind between two names (man and Joseph) is not the same as the difference between a name, surname or nickname, as in (Albert or Mr. Einstein or Mr. Genius).
Do you get what I mean?
In our day-to-day conversation, it is common to say, My name is Joseph or Jane or Anil or Asha. We use these names for ourselves. None of us says: "My name is a man" or "My name is a woman".
We don't usually think of man, woman etc as names. Yet in truth, they are names because we use those words to refer to people. Grammar recognizes this fact. So grammar is more true to life than life itself!
The answer to this question is that it depends on the criterion we use to distinguish one noun from another.