The process of creating 3D using Three.js could be likened to how a movie set works. You start with an empty stage and add some things to it to create a scene. For example, we could add some actors, props, and a backdrop so it looks like we’re inside. Each actor puts on a costume so they look like the character they’re playing. Lights are added so we can see and to set the mood. Finally a camera is positioned to shoot the scene from the desired perspective.
So the actors and props are made by a collection of vertices and faces, which combined is called a geometry. Then from this step, you assign a material to a geometry. A material can be a flat colour, or it could be a texture such as a photo of rock, or wood, or skin. When a geometry and material are combined you have a mesh. A mesh is a complete object that can then be added to a scene. You can move and orientate the whole mesh in your scene as a single object, but you can still access its individual parts if you need to.
Anyways, I can talk more about this another time, lots of work to do. Ciao for now.