A 3D map window comprises of a view type (Map, Globe, Orthographic, FirstPerson) and a set of 3D Layers.
Bitmap - A bitmap layer is a geo-referenced image shown on the map. PNG and maybe GEOTIFF are the preferred formats.
Vector- A vector layer is a 3D or 3D vector geometry shown on the map. We will usually be using GeoJSON as the format.
Terrain - A Terrain layer (or topographic layer) uses some elevation or other height data to represent the earth's surface by creating a 3D mesh.
In addition, a raster layer or a raster tile layer can be draped over the top of the mesh to show realistic terrain.
Finally Vector Layers can be rendered on top of the terrain or draped over the terrain.
Clip/Mask- A clip layer is a vector layer of polygons that masks other layers to only show their content that falls within the mask layer's geometries.
Labels- A point layer is used to render text on the map for labels.
Shape Scenegraph Layer - A shape layer is used to render 3D "symbols" at a given point on the map. These are real 3D objects with textured surfaces. Think windmill, cell tower, tree, etc.