Illustrators, on the other hand, produce the imagery that a Graphic Designer would use within their ‘structure’. It is their job to make sure that their illustration relates and visually communicates the same message as the content within that structure.
The setup is quite like a cheese sandwich. The Graphic Designer is the bread which holds everything together. The Illustrator is the cheese which must go well with the butter or lettuce or whatever else might be contained within the sandwich. Each to their own, though personally, I like a little mustard in there, but that is just me!
Without the bread, the cheese is still nice but it has no real place in the world. That is why the Illustration would possibly be considered as Art. But that is a ropey debate that probably won’t come to any real conclusion any time soon.