Depth textures are available for sampling in shaders as global shader properties. By declaring a sampler called you will be able to sample the main depth texture for the camera.

always refers to the camera's primary depth texture. By contrast, you can use to refer to the last depth texture rendered by any camera. This could be useful for example if you render a half-resolution depth texture in script using a secondary camera and want to make it available to a post-process shader.

In the Built-In Render Pipeline, the motion vectors texture (when enabled) is available in Shaders as a global Shader property. By declaring a sampler called '_CameraMotionVectorsTexture' you can sample the Texture for the currently rendering Camera. When sampling from this texture motion from the encoded pixel is returned in a range of -1..1. This will be the UV offset from the last frame to the current frame.