grayson
Assuming you've ordered a 6 Series Panasonic Display there is 1 x HD15 VGA connector built into the chassis of the display - this accepts PC (RGBHV) or YUV video signals.
The other D-Type socket on the chassis is a Serial port for talking to the comms port on your PC or to a control system such as AMX or Creston.
The chassis of your display has three expansion slots that can be populated with a variety of video input cards - the cards are rectangular (you did ask).
You can add a single slot HD15 card if you like or a single slot BNC terminal board (5xBNC for YUV or RGBHV) or the twin slot Combined board that offers you RGBHV on BNC + S-Video + Composite.
Alternatively you could add an external HD15 switch - I usually supply the Kramer VP-211NDS (£129+VAT) as it has selectable priority switching.
One advantage of adding a second card rather than the auto switch being you can have two sources displayed side by side or picture in picture if you go in on separate inputs.
Best regards
Joe