The document discusses an introduction to 3D web mapping using X3D within the context of free open source software for geospatial applications. It covers the benefits of 3D visualization, the technical standards and structures of X3D, and the functionalities of X3DOM for rendering 3D content in web environments. Additionally, it highlights challenges in 3D web representation, tools for working with X3D, and the integration of X3DOM for geospatial applications.