That field is a TextureDescriptor, not a TextureViewDescriptor. A single texture can be interpreted in multiple ways. It could be interpreted as a regular 2D image, as a cube map, as a 3D image and so on. You could use varying mipmap levels.You could have a single layer or multiple. And in the future it may be possible to interpret a texture as an srgb image at one time and a linearrgb image at another time. The TextureViewDescriptor describes how you want to interpret the texture for this specific texture view.