Relay To Isolate Wire From Lock/Unlock Switch?

Hi, Could someone explain what the notes highlighted in the box means..."Relay to isolate wire from lock/unlock switch". I'm just learning so would appreciate the help. Thanks,

What is the year/make/model vehicle? Here's an example of a relay isolating diagram, but probably not the one you need: https://www.the12volt.com/relays/relaydiagram3.html

The relay is used to isolate the vehicles lock switch from the aftermarket devices (-) Lock output signal. Here is a diagram for the added relay. Under normal operation the vehicles Lock signal passes thru the relay, Pin 87A to Pin 30. With a aftermarket Lock signal output, the relay is energized. This opens the normal vehicle Pink Lock wire path through the relay and puts a (-) on the vehicles Lock wire going to the Fuse Box connector only.Soldering is fun!

It's a Smart Fortwo 2008 UK model auto.

Thanks Kreg and Lee for taking the time with the diagrams and explanations; really helped my understanding.