How do puncture-proof tires work on cars?

Tires are not really puncture proof but instead are puncture sealing tires. The tire is built with a puncture sealant type rubber on the inside of the tire. When any object punctures the tire it goes through the material. When the object is remove the material seals the hole. This material has been used for years and does work but at a price. The tire is heavier and cost more to manufacture. There are also run-flat tires that have an internal blatter within the tire that prevents the tire from going completely flat.