Well, not sure about the rectangular one, but the others.....
white round one should be for a factory radio connection, and the black round one I think should be for a factory alarm system connection.
The reason I say should, I bought a radio harness(for my '97 without a radio) from a euro seller and the connection mated with the large black one.
My '95 has a (U.S. market)factory radio harness that connects to the small white one......