Sealcoat is a liquid that is applied to asphalt to protect it from oxidation and the damage caused by winter cracking, as well as UV rays and traffic. In areas of the world that experience freezing and thawing, the reapplication time line will likely be sped up.
Whether your driveway is concrete or asphalt, sealing it is an important part of keeping it looking like new for a long time. The sealant, which sits on top of the driveway, acts as a barrier that prevents water, ice, car fluids, the sun, salt and other chemicals from staining and eating away at the surface of the driveway.
The frequency with which you should use driveway seal will vary based on your location. Home-owners in climates with cold, harsh winters and numerous freeze-thaw cycles will have to seal their driveways every one or two years. Those in much milder climates can probably do it as little as every four years.