SDcard vs SDcard0

[rtbcomp]

I have the following folders on my tablet

\SDcard
\Storage\SDcard 0
\Storage\SDcard 1

I've copied these onto my PC and notice that SDcard and SDcard 0 are more or less identical. They have the same number of files and folders, SDcard is about 200 MB bigger than SDcard 0.

Are SDcard and SDcard 0 two different areas of storage in the tablet?
If I add a file to one is it added to the other?
To ensure my data is safe do I need to back them both up to the PC?

Thanks.

 

[mrsmumbles]

Back up to sdcard1 and computer. Sdcard1 is your microsSD card and sdcard0 is your phone.

Sent from my Nexus 5 using Tapatalk 2

 

[rtbcomp]

I realise what SDcards 0 & 1 are, it's the "SDcard" by itself that's puzzling me.

If "SDcard 0" and "SDcard" are the same, why refer to them with two different names, and why the difference in size?