I used to approach this problem from a slightly different direction with a view to answering the question - What is design?
I would ask students - What’s the difference between art and design?
And then I would flippantly say design is solving a problem. If you aren’t solving a problem, you’re doing art.
I know this isn’t precisely true but serves well to illustrate a point and I do explain this to the students.
My theory goes like this. Any man-made object (even art) can be analysed using the approach of examining its Form (shape, colour, material, size etc.), Function (what does the thing do and how well does it do it?), Feeling (what are the semantic and emotional properties of the item. Is it friendly, dangerous, dependable etc) and finally, Context (this is a reevaluation of the Form, Function and Feeling with regard to who is using it, and where and when it is being used).
This approach allows for an understanding of made objects without being didactic about it.
So is a poster for a gig, Art, or Design?
Well, it has form (Generally flat rectangular, with colour, maybe images and words), a function (Generally it will have two functions. Firstly, it needs to grab attention and secondly, it needs to communicate some information) and it will have a feeling (A rave poster feels different to punk poster and they both will feel differently to a classical music poster). And the context could by posted under a flyover, or on a teenagers bedroom wall or framed in a exhibition.
So it is definitely design. But it could also be art.
Art obviously has Form, Feeling and Context but does art have a function?
Well it could be decoration, that’s a function.
But probably the function of art is to provoke an emotional response (which might be different to the Feeling of the physical piece itself).
So, anything that has been mediated by someone can be art if that is the intention of the creator, or the perception of the viewer.