Long enough to reach the ground.
Football players wear cleats, these are shoes with spikes on the bottom to give better traction to the person wearing them.
Cleats. If you mean brands, different players wear different brands, sometimes depending on team sponsorship.
Jerseys. Jerseys shoes(cleats),pads,helmet and a mouthpiece. --------------- Some also wear pants.
You can wear soccer cleats to play american football but it is less than ideal. Soccer cleats do not have a stud on the toe of the cleat like football cleats do. This make it much easier to run, cut and dig into the grass. Most football cleats are also higher and more supportive than soccer cleats. Although if you are a field goal kicker/ punter or kicker in American Football - they all wear soccer cleats. Basically you CAN wear soccer cleats to play American football but you CAN NOT wear American Football cleats to play Soccer.
Despite its rough nature, Football players generally dont wear a lot of protection. Apart from their jerseys and cleats, they wear shin guards.