States (Direct3D 9)
A Direct3D device uses states to set-up all of the pipeline processing. Sampler states control the set-up of the texture samplers by defining texture addressing and filter modes for example. Texture states set-up the multi-texture blender which controls how textures are combined and blended with each other. Render states control most of the pipeline state.
State blocks are a convenient mechanism for saving and restoring state. See State Blocks Save and Restore State (Direct3D 9)