The concept of Reference Architectures is novel in the business world. However, many architects active in the creation of complex systems frequently use the term Reference Architecture. Yet, these experienced architects do not collectively have a consistent notion of what constitutes a Reference Architecture, what is the value of maintaining the Reference Architecture, what is the best approach to visualizing a Reference Architecture, what is the most appropriate level of abstraction, and how should an architect make use of the Reference Architecture in their work? This paper examines current Reference Architectures and the driving forces behind development of them to come to a collective conclusion on what a Reference Architecture should truly be. It will be shown that a Reference Architecture captures the accumulated architectural knowledge of thousands man-years of work. This knowledge ranges from why (market segmentation, value chain, customer key drivers, application), what (systems, key performance parameters, system interfaces, functionality, variability), to how (design views and diagrams, essential design patterns, main concepts). The purpose of the Reference Architecture is to provide guidance for future developments. The Reference Architecture incorporates the vision and strategy for the future. The Reference Architecture is a reference for the hundreds of teams related to ongoing developments. By providing this reference all these teams have a shared baseline of why, what and how. It is the authors' goal that this paper will facilitate further research in the concepts and ideas presented herein.