Padded things are stuffed with something soft for protection or comfort. A padded envelope keeps the contents safe, and a padded seat cushion keeps your bottom comfortable.
A padded bench is more comfortable to sit on than a wooden bench that's not padded, and a padded boxing glove protects a fighter's fingers. You can also use this adjective to mean "filled out or increased artificially," like when a recent graduate brings a padded resume to a job interview or a saleswoman submits a padded expense report after her business trip.