Analogy of clients and servers:
      -The relationship between clients and servers is that of a person and a vending machine. The client (person) finds the vending machine of the group that
      they are looking for (URL), then puts the proper amount of money in (authentication), then makes their selection and are returned a product (document, images, 404 etc).
      If the client needs another product to complete their meal they can make another selection at the same vending machine by following the same process.