Need help figuring out how to use my Debian Partitions

Greetings, I've installed my Debian Server over 4 months ago, I didn't quite understand what the paritions were for, but the server provider made my partitions. Anyway I was putting most of my files in /gserver and it ran otu of space quickly when in the store page it says 2tb I barely used 18gb and it ran out already. So I used DF -h and it seems that I got 1tb of free space in /dev/md/2 here is a picture I don't understand where I'm supposed to put the files, and I don't really understand how partitions work in debian.. All I understand is the root partition only has 18gb and where should I CD to if I want to use the dev/md/2 partition? Regards, Here is a picture of the df -h hxxp://i.imgur.co(m)/DgA06MF.png

---------- Post updated at 11:49 PM ---------- Previous update was at 11:49 PM ----------

Had to change http to hxxp and com to co(m) because it wouldn't let me put a url without 5 posts.

You can mount the /dev/md/2 on /gserver.
Edit /etc/fstab to configure the mounting for next system boot.
Note that the previous contents in /gserver is 'overmounted' i.e. becomes inaccessable.
You best mount it immediately with

mount /gserver

/dev/md/2 has been mounted in /data. um, why don't you just use /data for storage instead of /gserver ? /gserver is folder on 'root' partition, you shouldn't ever fill that one completely.