Why 5x120? Can others be done?

[sweetride01]

First off, I'd like to mention that I still don't understand everything about choosing a wheel (obviously).
After searching online for a bit, I found some good information on BBS wheels (which I seem to particularly like).
Can someone please explain the 120 part in 5x120? I'm guessing it's the distance from the centre, but I really don't know.
Can a conversion be done to 5x114.3? It seems like a load of the nice wide wheels have this spec.

[sweetride01]

Ok, well after finding an article on Tirerack, I understand the 5x120 stuff.
Can a conversion to 5x114.3 be done on an E30 though?

[Addissimo]

There wouldnt really be a point to do it unless you had rims for 5x114.3 already. You'd spend more money on the conversion then you would on the rims.

We do 5x120 because its BMW's bolt pattern, and we can use BMW parts from other cars without too much modification. I'm sure with lots of fabrication and mad welding skills you could convert to 114... but it'd be pointless.

-Addis