Is Costco (Nasdaq: COST) a retail company or a membership company? It does both, selling goods at wholesale prices while also charging its patrons an annual membership fee.

But Jim Sinegal, founder, chairman, and former longtime CEO of Costco, says there's no question that at its core, it’s a retailer. Last month, The Motley Fool’s own founder and CEO, Tom Gardner, ventured to a Costco warehouse in Florida for a conversation with Sinegal on business, leadership, and company culture. In the clip below, Sinegal explains its retailing roots, and who its most important customers are. (A transcript is provided below; running time: 1:15.)