Chargers are "plates" that are not meant to be eaten off of and are placed at each place setting as purely a decorative item. Chargers are usually removed prior to serving. At times, the appetizer course may be served on the charger but is then removed prior to serving the main course. Having a charger at each place setting completes the look of your table nicely. Chargers are also called underplates, chop plate, service plate, show plate (the name I was first taught years ago in banquets) or base plate.
Photo credit: J & J Photography