What is the little slot on the left side of my laptop?

[DrCAKE]

I have a Toshiba satilite (don't remember which kind) and it has a little slot on it and i was wondering what it was \:

 

[C12Friedman]

The little slot (it's on almost all laptops) is called a "Kensington Lock". The actual "lock" is sold seperately, it's simply the slot the lock goes into. Here's a wiki article about the lock.
http://en.wikipedia.org/wiki/Kensington_Security_Slot
If you're describing another slot, please clarify.