What are the long-term effects of caffeine?

I am a college student and I have been drinking at least two or three cups of coffee a day for the last 4 years. Back in high school I had an energy drink every other day. My parents tell me it's not good for me. I'm wondering if they're right. Could I be potentially harming my body in the long run? Or even now? Is caffeine, in general, bad for my health?