Shade smooth is a technique where we can make mesh look smooth without changing the mesh itself, this makes the model look higher poly while having the same amount of vertices. Here is an example showcasing different kinds of smoothing techniques in blender. You can click 5 in the keyboard to sqitch on the wireframe view. This is just a showcase of the different kinds of smoothing techniques in blender and what gets exported via gltf/glb. note: The shade auto smooth is like a modifier in blender and needs to be applied before exporting or it wont work.