Retail distribution
The illegal drug business or trade primarily consists of the cultivation, manufacture, distribution and sales of prohibited drugs.
Cultivation and manufacture involves planting and harvesting prohibited drugs from plant sources (e.g. opium or marijuana) and processing the plant raw materials to produce the final product. For synthetic drugs, manufacture entails securing (sometimes by importation) of the chemicals required for the production of a certain drug (e.g. methamphetamine). Importation of the raw materials or final products might also be necessary to meet the demands.
With the final product at hand, the next step is to distribute and sell the drugs -- wholesale or retail. Wholesale distribution and sales involve large amounts (in bulk) of the illegal drugs while retail involves smaller amounts.