A USDZ file is Apple's 3D format for augmented reality. It is a zipped package based on Pixar's Universal Scene Description (USD) that carries a model's geometry, materials, and textures in one file, and iPhones, iPads, and Vision Pro open it instantly in AR Quick Look, no app required. You can make one from a single photo on your Mac with 3D Mate.
AR Quick Look is built into iOS, iPadOS, and visionOS. Tap a USDZ in Safari, Messages, or Files and the model appears in your space in AR, correctly scaled, with no download. That system-level support is why USDZ is the format for sharing 3D on Apple devices.
USD is Pixar's scene format, used across film and 3D; USDZ is a zipped, AR-friendly package of it. glTF (and its binary form GLB) is the open web and game-engine equivalent. For that comparison, see GLB vs USDZ.
3D Mate generates a 3D model from a photo on your Mac and exports USDZ in a click, so you can drop a real object or a generated model straight into AR. See the augmented reality page and the formats overview.