Reference architectures have emerged as a special type of software architecture that achieves well-recognized understanding of specific domains, promoting reuse of design expertise and facilitating the development, standardization, and evolution of software systems. Designed for various domains and purpose, they have increasingly impacted important aspects of system development, such as productivity and quality of such systems. However, reference architectures have been sometimes established without an adequate concern about which elements they should encompass. Besides that, there is a lack of work that investigate the essence of reference architectures, their dimensions and elements that they should contain. In this perspective, the main contribution of this paper is to present a reference model for reference architectures, named RAModel (Reference Architecture Model), that intends to improve the understanding about what reference architectures are, as well as their components and relationships, supporting the establishment, use, and evolution of such architectures.