What are the numbers for a track chain/cog relating to for dimenisions?

Ive seen sizes for track (fixed gear) cogs that say to use a 1/2" x 3/32" and 1/2" x 1/8". What do these numbers mean? Or even simplier, will a standard Shimano 10spd chain fit either of these? I'm trying to convert my tri bike to a fixed gear for a time trial. Ive got everything else but a cog and maybe a chain, if I have to buy one. Any help is appreciated.