Larger than a dinner plate, a charger plate is purely decorative and is placed beneath the plate holding the food. Chargers are usually reserved for special occasions.
Do not place food on the charger plate!
If you think of the charger plate as a place mat or a table accent, you’ll have a clearer idea of how one is used (and thus avoiding any potential embarrassment from using one as a dinner plate!).
The charger plate remains on the table throughout the meal service while the plate/bowl with the food is used and then replaced throughout the various meal courses by the wait staff.