In recent years, the topic of data spaces has been increasingly gaining traction. Multiple research initiatives, backed by industrial and government actors have introduced several data spaces for various industries and medicine, and beyond. In order to support value creation, public services and collaboration between a plethora of different participants of the data spaces, the sharing of information and building services and insights thereupon has been identified as key enabler. However, these initiatives differ in various properties from the initial idea for data spaces derived in research. In this article, we review the current state of literature regarding the concept of data spaces and the impact of European initiatives, namely International Data Spaces, Gaia-X and European Health Data Space, on the literature. Identifying characteristic properties of data spaces and its participants, we provide a general overview.