This document discusses the makeup and thinking process of customers. It defines customers as individuals or businesses that inquire about or purchase goods and services. There are two major types of customers: internal customers within an organization and external customers who are end-users. External customers can be existing customers who have purchased before, former customers who previously purchased, or potential customers who have yet to buy but may in the future. The customer thinking process involves recognizing a problem or need, searching for information, evaluating alternatives, making a purchase, and assessing the purchase after. Understanding how customers think enables better relating to and serving customers at each stage of the buying process. The document emphasizes that customers are very important to any organization's success.