gltf to fbx conversion is used for the purpose of converting 3D models between two different formats. Not every 3D modeling tool actually supports GLTF formats, but quite often plugins are available that allow import of these models and possible export to another format. FBX is common enough, so Blender (with plugin) or even the FBX converter provided by Autodesk should be enough for this task.
Updated: February 27, 2023