help understanding android file structure

[m147]

ok, in my root folder I have /mnt and /storage. what is the difference between the two? in /storage/emulated I find /0 and /legacy. I compared both folders with es explorer and they're both exactly the same file, folder and byte-wise. does this mean it is taking twice the storage space? also under /mnt/shell/emulated I also find /0 and /legacy. however, here /legacy is empty and /0 does not match the one under /storage/emulated. please help me makes sense of all this. thanks.

running 4.2.2 by the way.

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