Retailer is supermarket or hypermaket or any shop that want to sell online to shoppers.
Distributors sell products to retailers in the same country.
Wholesalers sell products to retailers and distributors in different countries.
Farmer produce fruits and vegetables and sell to distributor and wholesaler in the same country.
Importer buys fruits and vegetables from exporter in different country.
Exporter sell fruits and vegetables to importer in different country.