Android External Storage: What is the difference?

I would like to find the path for the external storage, so I use the following:

File[] dirs = ContextCompat.getExternalFilesDirs(this, null);

In returned I get the Array of:

dir[0] = "/storage/emulated/0/Android/data/com.example.proj/files/"
dir[1] = "/storage/12FE-350D/Android/data/com.example.proj/files/"

What is the difference between those two items ? And if I want to store images, which one is better to be used ?

Thanks for some highlights.