why do I hear a click by the gear shift when I apply the brake pedal on 1999 Lexus LS400

and my 1999 Lexus LS 400

2 answers
There is a lock that prevents removing the shifter from "park" if you do not have your foot on the brake. The click you feel/hear is the lock disingaging to allow you to move out of "park".
That's the shift lock release.