As with any other wart on your body, they are caused by human papillomavirus, and yes, they never truley do go away.  You can get treatment for existing warts (like freezing them off), but the virus will still hang out and pop a wart up whenever it feels like it.  Of course, the virus may also stay latent for the rest of your life, and not ever produce another wart.
The same goes for genital herpes.