Overbite. In layman's terms, an "overbite" typically refers to the upper front teeth sticking out horizontally, further than the lower front teeth. An orthodontist defines an "overbite" as the vertical overlap of the upper front teeth over the lower front teeth. They are very different situations unfortunately with the same name. It's best to have an exam with an orthodontist to determine the problem.
Braces. It really depends on how severe of an overbite you have. 1-3 years would be an average.
Depends. This totally depends on a case by case basis as well as if anything else needs to be fixed. Typically not just an overbite needs to be fixed but things like your occlusion (how you bite) also needs to be fixed. Treatment times can vary from anywhere from 6 months to 4 years.