Like D1211 said, it is a painless, fairly routine office procedure ( I'm having one this afternoon at my ENT visit, followup for tonsil cancer). It gives your ent a top down view of your throat, you may be asked to move your tongue or swallow. It usually only takes afew minutes. It's a quick and easy way to look for things that could be causing your symptoms, not just cancer. If they do suspect cancer, they might take a biopsy, that can be done in the Dr.'s office too.
Best wishes.
Mike