glTF (derivative short form of GL Transmission Format) is a file format for 3D scenes and models using the JSON standard. It is an API-neutral runtime asset delivery format developed by the Khronos Group 3D Formats Working Group. It was initially intended to be an efficient, interoperable format with minimum file size and runtime processing by apps.
Being called ‘JPEG of 3D’, GLTF is indeed a star of 3D model formats. Standard for many 3D applications and game engines, it is especially prominent as a common publishing format for 3D content tools and as the format of choice for web apps.
A PRT file is a model part file saved in a three-dimensional model format used by Unigraphics, a 3D CAD program. It contains surface and solid information for a single part. PRT files are saved in a binary format, similar to an Alias wire model and an SDRC (Structural Dynamics Research Corporation) model.