Not all horses run their best on every type of track, which can make a real difference in handicapping and betting outcomes. Tracks essentially come in two types: dirt and turf, the latter covered in grass. Dirt tracks can be much faster than turf tracks in dry conditions but slow considerably in the rain or when otherwise wet. Turf tracks can be slower than dirt tracks in perfect, dry weather, but they do not slow down as much in the rain, since the grass helps drain water and hold the surface together.