Wholesale distributors are traders or merchants who buy the things directly from the manufacturers, producers and farmers in the case of agricultural products, and sell the same to retailers for eventual sale to general public. The difference between the rate at which they get the things from the manufacturers and the rate at which they supply it to retailers is their earnings or profit.
Similarly, the retailers sell the same in small quantities as required by the general public. Here again, the difference between the rate at which the retailer gets the goods from the wholesaler and the rate at which he sells it to his customers becomes his earnings or profit. It may vary for both of them based on the demand of a particular item.