Converter takes 120V AC power and 'converts' it to DC to supply DC power for the 12V DC System AND provide a charging circuit for batteries.
Good idea to have a Surge Protector that tests/verifies AC Voltage, tests for loss of neutral/ground, trips on Hi & Lo AC Voltage etc.
EMS.Energy Management System may be a function also.....course your RV may already have an EMS....monitors AC Line Voltages and sheds load based on AC Power Source.