Explanation should include the selection process:

Process/Skill Questions:

How are vendors chosen?
What quantity, quality, and delivery frequency are required for vendors?
What are the advantages of buying from a single supplier? From several suppliers?
How might building a relationship with vendors prove beneficial for the retailer?
What factors best facilitate effective buyer-vendor relationships? Why?
What methods are used to find and meet potential vendors?
Why is it important to request product samples before making a final vendor selection?