Difference between log and linear

With log and linear pots, I know what each pot does differently but what is the actual physical difference between them? Can one be made into the other? Just curious.

http://www.geofex.com/Article_Folders/potsecrets/potscret.htm

Thanks Shepherd. Some high end stuff there for my little brain, but I think I understand.

As a side note, I love the eternal debate about log and linear pots when probably 75% of players turn everything to 10 and go.