The wikipedia page at https://en.wikipedia.org/wiki/Free_and_open-source_graphics_device_driver https://en.wikipedia.org/wiki/Free_and_open-source_graphics_...

The wikipedia page at https://en.wikipedia.org/wiki/Free_and_open-source_graphics_device_driver https://en.wikipedia.org/wiki/Free_and_open-source_graphics_... has some somewhat helpful graphics at least explaining the relative abstraction levels of the different entities.