The standard
writing (sometimes also
art) must meet before it can be published. Not all
publishing outlet set their publishable
standard at the same
level.
Vanity press will by
definition publish almost anything. The
Encyclopedia Britannica in
contrast only publishes material of a very
high standard.
When young writers are working to get their first writing published they usually submit it to outlets (newspapers, magazines, journals and compilations) at the lower end of the market (i.e. with a lower publishable standard) and work their way up to the top end. As writers skills and experience increase they are more likely to have an idea of the acceptable standard for a given outlet.
Some very-high-end outlets only publish work by established writers; when writers get their work accepted to such places they have arrived---they are no longer journeymen.