A wart is a growth on the skin caused by the human papilloma virus. They're usually contracted from contact of broken skin with a person who also has the condition. They're usually harmless, although they can last for years and can also disappear and recur. They don't require treatment, although there are treatments available.
The new HPV vaccine, generally administered to prevent cervical cancer, is also effective against warts.
About 75% of warts can be cured in 7-10 days by applying a topical preparation of salicylic acid. Cryosurgery has been tried as a treatment, but isn't seen as a more effective treatment and often requires several visits. Other treatments are either expensive, have little supporting clinical evidence, or aren't FDA approved.