A fixed gear is a single speed bike that doesn't coast. Most have flip-flop hub that will let you put a fixed cog on one side and a freewheel on the other. Whether you go fixed or free, if you ride on the street, you'll need a brake. If you live somewhere flat, like Chicago, one gear might be all you need. I commuted for a bit on a fixed gear (Sacramento might be even flatter than Chicago) and it was perfect. I gave it to my son and he commuted to HS every day, rain or shine. Simple, reliable, bombproof.

You might want to post this in the FG forum.