[PC-BSD Support] Why are there two /tmp dirs in Free/PC-BSD ?

[USM Bish]

Looks like a newbie question. Sorry for looking naive ;-)

Why are there two /tmp dirs in Free/PC-BSD ?

Besides /tmp there is also a /var/tmp

I tried to experiment a bit by moving the contents of /var/tmp
to /tmp and then deleting it. I created a soft link of /tmp to
/var/tmp.

On reboot I got stuck up at the boot prompt of KDE, which kept
on re-appearing even if correct username/ password was entered
Quite obviously, KDE failed to create the orbit dir of user or
dbus links of KDE failed.

So I reset things to  normal by re-creating the /var/tmp after
logging in from console (ofcourse,  I needed to chmod /var/tmp
to 1777 to get things back  to normal, which I learnt the hard
way ;-)

But this  kept me wondering  why a soft  link to /tmp  did not
work. And why two dirs for temporary files ?

Bish