MEDIA_ROOT，MEDIA_URL，STATIC_ROOT，STATIC_URL和ADMIN_MEDIA_PREFIX的文档定义是什么？

I have read something about them via official doc and some posts, but I'm still confused. As far as I now can see, MEDIA_ROOT is for user uploaded images and files and STATIC_ROOT for js, css, etc. As for MEDIA_URL, is that for retrieving images? And is STATIC_URL for linking js and css?I have read something about them via official d