Wikipedia contains articles on people who are famous for many different reasons. But in order for someone to be the subject of an article in Wikipedia, only two things need to have happened:
1.Someone has written the article.
2.There has been no consensus to delete it, at least not yet.
That's all. So from time to time Wikipedia contains articles on people who are not famous at all. Most commonly these are articles written by the subjects themselves. There are several reasons they do this:
To promote a career in music or other forms of entertainment.
To help to create an identity, perhaps to support fraud.
Because of delusions that they are famous, which may be mere eccentricity or may be a sign of mental illness.
Because they haven't yet read or understood what Wikipedia is not.
Any one of these is sufficient on its own, but often it is a combination of two or more, or even all of them. And there are other reasons too, but these are the main ones.
Wikipedia discourages people (however famous they may be) from contributing articles about themselves. Genuinely famous people will have others wanting to write about them. However, it's very hard to police this, especially as we are very happy to have genuinely famous people update existing articles about themselves.
Less commonly, these articles may be written by other people, again for various reasons, some of them more innocent than others.
Wikipedia practices a limited amount of tolerance towards these articles, whoever writes them. Exactly how much tolerance is good is the subject of a vigorous and ongoing (and possibly never-ending) debate. Some challenges these articles present are:
Some people create multiple websites and userids in order to give a false impression of fame. They may write unfavourable as well as favourable reviews of their privately published or non-existent work. (Genuinely famous people are most unlikely to find the time for such things, of course.) While we have methods of identifying these, they are time-consuming and fallible.
The definition of exactly who is famous is problematic, and as Wikipedia is not paper there is no reason to delete genuinely borderline cases.
Some borderline cases are people who are not yet famous but will be soon, and it is impossible to predict who these are.
Articles which link to this page are ones that someone has suggested are about a person who does not really qualify for a Wikipedia article. But again, this is no guarantee that the subject of the article in question is not famous. It just means that someone thinks they are not and wants to warn you to consider this carefully. Whoever this is should have put their reasons in the article's talk page, which is accessible through the Discuss this page link at the bottom of the article in question.
The suggested text for linking to this page is:
It has been suggested that this article is about someone who is not famous. You should exercise caution in relying on this information.
which is produced by:
''It has been suggested that this article is about someone who is [[Wikipedia:probably not famous people
not famous]]. You should exercise caution in relying on this information.''
As yet there is no Wikipedia approval mechanism. Whether there should be, and what form it should take if so, is also the subject of ongoing discussion.