There is only one file type that uses the .USDZ extension:
Universal Scene Description Zipped Format
A USDZ file contains a 3D scene or object saved in the USDZ Universal format, which is developed by Apple and Pixar Animation Studios. It is an uncompressed and unencrypted .ZIP archive that stores a Universal Scene Description (.USD, USDA, or USDC) file, which includes 3D geometry and shading data. USDZ files may also contain .PNG and .JPEG image textures and .M4A, .MP3, or .WAV audio files utilized in the 3D object or scene.
Updated: January 17, 2020