basically its what ATC uses when they don't have radar. there are some requirements; missed approach can't have a course reversal(i.e. the missed is a straight out or opposite direction from the IAF), no PT for the approach, and a couple others

they start one AC on the approach, and after a set period of time, start the second one on the approach, then after a set period of time... (wash, rinse, repeat)

the time is based on your approach speed, the speed of the guys in front and behind you, and the winds.

hope that helps