Warts are an infectious disease of low infectivity caused by a virus. They may occur anywhere on the body but are frequently seen on the hands, feet, and face (areas of frequent contact). Warts may be named by their location and appearance. On the soles of the feet they are called planter warts. Around and under the fingernails or toenails they are periungual or subungual warts, respectively. Common warts on the hands, arms, legs, and elsewhere are verrucae vulgaris but often just called common warts. Numerous very small smooth flat warts (pinhead size) often seen in large numbers on children's faces, foreheads, arms and legs are called verrucae planae juveniles. These are seen less often in adolescents and seldom in adults.

The typical wart is a rough round or oval raised lump on the skin that may be lighter or darker than the surrounding normal skin, skin colored or even (rarely) black. Most parents are familiar with the look of a typical wart and have little trouble in diagnosing the condition. Warts with a smooth surface and the small flat warts in children may cause some difficulty in diagnosis for the average parent. Common warts cause no discomfort unless they are in areas of repeated trauma.

Plantar warts are no different than the common wart but, because of their location on the soles of the feet, they tend to be deeper and can become painful. Large numbers of planter warts on the foot may cause difficulty running and walking and can be debilitating.

Warts around and under the fingernail are similar to the common wart but much more difficult to cure.

The common wart may disappear spontaneously, often within 2 years of its appearance. Because people generally consider warts unsightly and there appears to be a social stigma (among school children) associated with having warts, parents often seek treatment. Treatment of warts has improved significantly in the last 10 years but even with effective treatment recurrence is not uncommon.