The competition port is used only in
in competition [edit] or simulating competition [/edit]. I'm sure there's a section in the manual that explains the different ports of the OI.
You walk up to the player station and plug in. This provides power to your OI and gives FIRST control over when you do or don't have control of your robot.
[edit] Mr.Bill Gold has also reminded me of the fact that "you can use the competition port to disable your robot, and put it in autonomous mode with a dongle." This requires wiring your own dongle, etc. Do not do this unless you know what you are doing.[/edit]
Here is the Innovation First pdf on how to do it properly:
http://www.innovationfirst.com/FIRST...nout_Guide.PDF