What is the difference between SoCal Approach, SoCal Departure and SoCal TRACON?
SoCal TRACON (Terminal Radar Approach CONtrol) is the name of the facility.
SoCal Approach and SoCal Departure are the call signs used over the radio by that facility, depending on whether the particular aircraft they’re talking to is arriving or departing. They’re the same controllers on the same frequencies.