It can be a bit subjective working out where the cutoff between Improver and Intermediate is.
Improvers - a bit more technical working to build up the use of spins and spending more time explaining the techniques around how to do this.
Intermediate - players are looking to improve their matchplay and are competing (at least in friendly matches fairly regularly). They would know how to hit slice / topspin
already and be looking to refine this and incorporate it into match situations.