What is "/dev/mapper/ubuntu--vg--root"?

I installed Ubuntu 14.04 recently. During the installation I did not create a separate partition for my home folder. I also accidentally encrypted my home folder. When i did

sudo df

I got the result as

Filesystem Size Used Avail Use% Mounted on
/dev/mapper/ubuntu--vg-root 455G 181G 251G 42% /
....

Why does this have a funny name instead of a normal '/dev/sdx'?

Please explain to me what this is?

1 Answer

The /dev/mapper/ubuntu--vg-root in place of a traditional /dev/sdxN block device just indicates that you chose to install the system using LVM2 logical volume management. See What is LVM and what is it used for?