A contact lens is a thin, curved lens placed directly on the surface of the eye to correct vision problems. They are often made from soft plastic materials that allow oxygen to pass through to the cornea. Contact lenses can correct various vision issues, including nearsightedness, farsightedness, and astigmatism. These lenses come in different types, such as daily disposables, which are worn for a single day, and extended wear lenses, which can be worn overnight. Proper care and hygiene are essential to prevent eye infections and ensure comfort while wearing contact lenses.