The publisher wants to hire the artist...
They want to choose an artist whose style they like-- possibly someone they've worked with before, possibly someone who's won awards or has a great track record. They'll want to enter into a contract with the artist for the rights to the work, and give specific direction for page counts, style, colors, size, etc.
Thanks for this information. I'm a neophite. An aspiring writer. I keep on thinking about possible illustrations that would go with my story when in fact, it's not really necessary.
Again, thanks a lot for this post.