Everything. If your are taking several medications they might have interaction between them and cause you unwanted symptoms. They might also have a side effect. If you came to the office and needed a treatment for your problem, physician need to choose the right medication for you to avoid interactions with your current medications, herbs, supplements, over-the-counter, etc.
A complete list. The name of the med, why are you taking it, how many times, the route of administration, any side affects and is it helping you for what you are taking it for. You should bring all medications to each visit including inhalers, vitamins, natural, and/or herbal medicines.