Your vehicle may be wearing boots right now and you might not even know it. They're called ball joint boots. They're actually protective, flexible things that protect parts of your suspension (called ball joints) from all the hazards the road can fling at them. If one of those ball joint boots fails and you don't get it replaced, the ball joints themselves could wind up failing, a repair that can be even more expensive.
Ball joint boots not only keep things like rocks, salt, water and dirt out of your ball joints, they also help the ball joints keep their lubrication inside and working properly. To do that, the boots have to be made of a flexible material, sometimes rubber, sometimes a synthetic. They do take a beating, exposed to temperature extremes and debris, and eventually they can tear or crack just because of their age. Unless someone is keeping an eye on your ball joint boots, you may never know there's a problem. That's why when you regularly take your vehicle in to a repair facility for other things like oil changes and routine maintenance, a technician will inspect the ball joint boots to make sure they're still in top shape.
If they're not, your service advisor will let you know. Take care of that soon and you may avoid having to replace the ball joints themselves or other suspension parts which may be much more expensive. Often it's best to replace boots on both sides of the vehicle since they frequently wear at about the same rate.
If you want to make a fashion statement, some ball joint boots come in various colors other than run-of-the-mill black. And some aftermarket boots are made of a more durable material than the original equipment that came on your vehicle. Some drivers get a real "kick" out of flashy ball joint boots!