what does this mean

I saw on the database for the 89-91 ford thunderbird security information the door locks say reverse polarity and for door unlock:  w/keyless negative trigger.

does that mean they are both neg if the car has keyless entry and rev pol. if not. or is lock ditterent then unlock. 

You got it. Ford uses two different systems for the same model vehicle. If the car has keyless entry, then both the door lock and unlock are negative trigger and if you DO NOT have the keyless module, you have a 5 wire reverse polarity system.