A virus that can be sexually transmitted. There are many different strains of HPV. Most strains don't cause any symptoms at all, so people don't even know they have it. However, other strains can cause genital warts or increase a woman's chances of getting cervical cancer.
Miko, I think getting tested again would be a great idea. If I were you, I would sit my partner down, explain it all, and educate him about HPV. As you said, it is very common. If he freaked out when you told him about your friend having it, he might not realize just how common it is. Maybe some wesbites or pamphlets from your doctor could help you explain it to him.