From early pregnancy – at around seven weeks - a plug of mucus seals your cervix to help prevent infection – hence the name, mucus plug. The mucus plug accumulates at the cervix during pregnancy. When the cervix begins to open wider, the mucus is discharged into the vagina and may be clear, pink, or slightly bloody. Labor may begin soon after the mucus plug is discharged or one to two weeks later.
Dilation, the opening of the cervix (measured in centimeters), and effacement, the thinning of the cervix (measured in percentage), occur in a pregnant woman as labor and delivery get closer.
I'm sorry your doc isn't explaining anything to you! Dilating is talking about your cervix, it is usually tightly closed to where you can't put anything in the opening, kind of like if you were making tight kiss lips. In order for your baby to pass through, it needs to open up to 10 centimeters, which your doctor will feel for. So each centimeter means your a little bit closer to baby passing through. Your mucus plug is inside your cervix and helps to keep bacteria out during your pregnancy, when it starts falling out it can come out in big globs or smaller pieces, it's usually clear/tan/yellowish in color and is like really thick snot, almost solid even. Usually when it's really time and you begin to lose your mucus plug it is tinted pink with blood which is normal and just means things are moving along in labor. I hope I helped, as I am no doctor, just a second time mommy(: