ok, you need to read this http://sheldonbrown.com/fixed/index.html and this http://sheldonbrown.com/gears/ will tell you about gear ratios (make sure you select 'gear inches' in the 'gear unit' dropdown).

1/2 x 1/8" means 1/2 inch pitch (the spacing between the rollers on your chain, and the industry standard.) and 1/8" means the the chain is 1/8 inch wide, which is pretty much standard for track chains (it's sometimes -- incorrectly -- called 1/8" pitch).

road chains are 1/2 x 3/32"; the pitch is the same as a track chain (rollers are 1/2" apart), but the chain is 3/32" wide.

you can run an 1/8" chain on 3/32" cogs and chainrings, but not the other way around.