What are `storage/emulated`, `mnt/sdcard`, `storage/sdcard`?
"In the case of devices without true external storage, it's still necessary for Android to provide an emulated external storage in order to remain compatible with older apps. In other words the RAM is physically internal (non-removable) but a section of it is partitioned and the Android file-system APIs treat that partition as being "external" and world-readable."


Taken from answer by @Squonk https://stackoverflow.com/questions/23625104/storage-emulated-legacy-vs-storage-emulated-0-vs-data-data-myapp



As to where to store your downloads at storage/sdcard. The others are symlinks to that location.



A symlink is a shortcut, a low-level pointer. A symlink will look like the linked file is actually there, rather than it just being a shortcut. Once you tap on it, it’ll be directed toward the actual file location and run/use data from there.