One use case is IO bound applications. Similar to NodeJS which can handle 10K concurrent IO calls on a single thread, python releases the GIL on IO. So you can

One use case is IO bound applications. Similar to NodeJS which can handle 10K concurrent IO calls on a single thread, python releases the GIL on IO. So you can write pure python and have multi threading and have all the benefits of "parallelism" depending on whether or not python releases the GIL which it does with certain libraries and on IO. For all else use multiprocessing.