Thanks I found some at a place in town!Grit is what chickens, and most birds for that matter, need to digest their food. Since they don't have teeth, they eat insoluble things like rocks that go into their crop so that when they eat food, it first goes through the crop to be ground up by those rocks and easily digested. They need grit if they are eating anything other than crumbles. You can buy it in bags at the feed store, or your chickens will just pick it up off the ground in forms of sand, dirt, and rocks. Your chickens know that they're supposed to eat grit so they will try and get it however they can. Most people just supplement it with bought grit to ensure they have a healthy supply of it for their crop.
Edit: I was corrected that the grit goes to the gizzard to grind up food, not to the crop! Sorry for the mistake!