The line is blurred, but I would say that illustration and graphic design can be differentiated by how and where you use them.
Illustration, to me, results in fine art whereas Graphic Design leans more towards commercial advertising. A good way to think about it is to ask yourself if someone might hang the work on their wall. If the answer is yes, then there is a good chance that it’s in the Illustration category.
Feel free to check out my dribbble or Instagram social media channels to view more of my work. You will be able to get a better understanding of whether or not my illustration abilities will meet your needs.