Merry Christmas for starters. I new to this and I need some help. I've been looking at diferent train sets for a couple of months now and this morning I unwrapped an Lionel, 6-30018, Pennsylvania Flyer O Guage starter set. It says fast track on the box but I have no idea what that means. Also, is this an O-27, an O-42, or an O? And what's the diference in them and are they interchangeable? Any information would great.