Are coldsores herpes?

Do coldsores mean that you have Herpes? My friend told me that coldsores were a sign of an STI. I had my first coldsore when I was 9 years old and I was definately not sexually active. I haven't had one since but I am afraid that I might be carrying Herpes. I know lots of people who get coldsores on a regular basis and I just don't understand how all these people could have Herpes....