My Dr did it with both my babies at 38 1/2 weeks had them within the next couple of days. I walked a lot after though and nothing will happen unless your body is ready.
They separate the bag of water from the uterine wall. They don't break the bag. Not all doctors do it and most wait until you are well past your due date.
Ot is when your Dr or midwife puts there fingers up your cervix and the swipe the amniotic fluid sac. You usually get it done at 40 weeks. Thats when I got it done.