Query re: disk free (df) output

[andy <geek_show@dsl.pipex.com>]

Hey all

Quick questions about the output of df -lh on a single-user Etch:

Filesystem            Size  Used Avail Use% Mounted on
/dev/hdb1              12G  3.7G  7.8G  32% /
udev                   10M   96K   10M   1% /dev
devshm                443M     0  443M   0% /dev/shm
/dev/hdb3             169G  4.3G  156G   3% /home

What are "/dev" and why is "shm" a sub-folder of /dev mounted separately?

Being new to Deb it's just one of a distro-specific curiosity perhaps?

Anyway, just curious if anyone has any thoughts.

Cheers and compliments of the season to those who recognise it.


A