Most wholesalers are classified according to
  • the MERCHANT services provided,
  • the MERCHANDISE sold, and
  • the TRANSPORT used.
Wholesalers can fit into more than one category. A wholesaler might be a limited-service, specialty-line, cash-and-carry wholesaler, for example. 

 
However, understanding how wholesalers are different is more important than being able to recall the names of the various wholesalers.

And, all wholesalers either improve exchange efficiency, or provide the specialized skills required to successfully complete exchange process transactions.