This is a far better explanation than the usual opaque "it's concurrent but not parallel" that I'd argue isn't even correct (cause two C calls on separate threa

This is a far better explanation than the usual opaque "it's concurrent but not parallel" that I'd argue isn't even correct (cause two C calls on separate threads are running in parallel if they don't hold the GIL). Or "it's multithreading but not multiprocessing" which misses the point.