Yeah the alarm one keep's the alarm on whist you can leave a child in the car , say your nipping into the shop for a paper you flick the switch so it lights up red and lock the car the alarm will be on but child can wave arms etc in the car , it will only go off iff a window or door in broken into ...
And like boydie says the other is so a breakdown truck can tow your car off without the alarm screaming but also locked ...