In a project, there may be times when text needs to be created as part of a 3D scene and not just in the HUD. Godot provides two methods to do this. The Label3D node and the text mesh for a MeshInstance node.
This page does not cover how to display a GUI scene in a 3D environment. For information on how to do that see this demo project.
Label3D behaves like a label node but in a 3D space. Unlike label node this can not inherit properties of a GUI theme. However its look remains customizable and uses the same DynamicFont and BitmapFont subresources control nodes use.
Label3D has minimal interaction with a 3D environment, it can be lit up and shaded by light sources if the shaded flag is enabled, but it will not cast a shadow, even with cast shadow turned on under the nodes GeometryInstance3D settings. This is because the node is a quad mesh (one glyph per quad) with transparent textures and has the same limitations as Sprite3D. See this page for more information.
Text meshes have similarities to Label3D. They display text in a 3D scene, and will use the same DynamicFont subresource. However text is 3D and has the properties of a mesh. A text mesh cast shadows onto the environment and can have a material applied to it. Here is an example of a texture and how it's applied to the mesh.
There are two limitations to text mesh. It can't use bitmap fonts, or fonts with self intersection.