Why are there four SD card 'locations' in the file manager?

[Purpur]

In my root directory there are these folders:
- sdcard
- sdcard2
- storage
in the storage directory there are these subdirectories
-- sdcard0
-- ext_sd
-- emulated

How come there aren't just two options: internal and external SD?

And what are the function of the folders I mentioned above?

 

[Purpur]

If these are what you would call symlinks, how do you check which are real folders and which are symlinks?

 

[Purpur]

Anyone?