I am a Belgian student writing a thesis about the candy sector in the US. An important part of the thesis are the many types of outlets that sell candy. I have a problem understanding the difference between all of these types. Could somebody please explain the difference?

The most important outlets are: supermarkets, department stores, mass merchandisers, convenience stores, drugstores and grocery stores.

Is a supermarket an example of a mass merchandiser?

For example "The Simpsons": what type of store is the Kwik-E-Markt?

At the moment I see no difference between a convenience and grocery store.

I thought drugstores sold only drugs (medicine)

Etc

Thank you very much for your cooperation