They are like warts elsewhere, but they grow inward. The wart cannot grow outward because of weight placed on it when you stand. You may experience severe pain when walking, and can have just one or many plantar warts. Plantar warts can stay on feet for a number of years and are difficult to treat. There are many over the counter medicaments available to treat Verrucae which have varied success rates. Other ways to treat Verrucae are Cryotherapy, Silver Nitrate, Salicylic Acid or even surgery.
There is no guaranteed success with any of these treatments. All treatments are designed to help stimulate an immune response from the patient so that their own immune system will recognise the verrucae and eradicate it.