为什么使用Nginx运行Flask需要WSGI包装器？

So from the Python/Flask docs, they both recommend not running the Flask web server as the production web server which makes sense. My question is, am I then able to run my Flask application on top of an Nginx server? Why do all the guides on the internet recommend wrapping Flask around uWSGI, Tornado, or some other WSGI server? What does it mean for something to be WSGI? Isn't Flask WGSI compliant?So from the Python/Flask docs, they both recomm