It's where you take an allotted time (an hour at the end of the day is usually recommended), lie down with a cold drink, and all you do for that time is concentrate on noticing the baby move and counting each movement you feel. Usually (I think) they want 10 (or more) movements in that hour. It's generally a way of making sure the baby's doing well without having to do a non-stress test (NST). If your baby's movements fall short, then the doctor will probably have you go for a NST (where they hook you up to monitors like when you're in labor, but just to monitor baby's movements).