For most consumer products, the user has purchased the product for their own personal use. But for many products, the end user and the buyer are not always the same.
End users are the people who will use the product in a hands-on manner a day-to-day basis.
The buyer is the person (or committee) who makes the final decision to purchase the product.
For enterprise software such as a call center management application, executives make the decision to purchase and install the system, but these executives usually never operate the software themselves.
Similarly, educational computer games for young children are not purchased by the kids themselves. Children may influence the purchasing decision, but it is the parents or other adults who buy the product.
Products purchased as gifts are another example of where the buyer is not the end user.
So while user experience design and usability testing must focus on the needs of the end users, your product must also simultaneously appeal to the potentials buyer, or it will never sell. Market research to understand buyers’ expectations and concerns is important and can strongly influence the scope and design of your product.