Effaced or effacement is basically the thickness of the cervix. When doing vaginal examinations things that the dr/midwife are looking for are dilation (how far open the cervix is), effacement (how thick the cervix is), position of the baby and the vaginal station which is where the presenting part of the baby is in the pelvis (how low it is). These things combined usually give you a good indication of the progression of labour or if spontaneous labour is likely to commence within a certain time frame.