A podium is a raised platform like the kind Olympians stand on when they win a medal or like the overturned crate in the garage where you pretend to accept your Academy Award.
Stepping up to a podium means taking center stage. A person might be receiving an honor or giving a speech and the added height of a podium makes that person the focus. If you wave a baton as the conductor of an orchestra or band, you'll need to stand on a podium so the musicians can see you. And, if you deliver a rousing message in a church you might use a podium, but probably shouldn't be waving a baton.