Sparrows are ground vehicles that Guardians use for fast ground transportation. Guardians just as often race as they simply travel between locations.
Sparrows normally come in two varieties: Trick and Speed. Trick Sparrows have a higher top speed and can be stunted on to recover energy. Speed Sparrows have a lower speed, but have a very powerful booster that launches them ahead at the cost of structural damage.
The Sparrow Racing League has a number of official sparrows which are uniquely crafted.