This book is the sequel to the previous one " Why Do You Buy ? ". Now we complement the understanding of the process of Purchase / Customers and Sale / Supplier in this dynamic chain that is the Market. Thus, we realise that Relationship Marketing aims to develop a lasting relationship with customers and partners seeking to value this interaction in order to achieve mutual goals, and still understand the application of CRM - Customer Relationship Management identified what steps are needed to implement Relationship Marketing in the retail sector.