@thenameisweasley
Effacement of the cervix
Your cervix not only dilates during labour, it also effaces. This is when it becomes shorter, softer and thinner.
When women have had lots of babies the cervix usually dilates and effaces simultaneously.
When you're having your first baby, all those latent phase contractions you have are working on effacing your cervix. So when you get to labour ward and discover (after two days of contractions) that you're "only" 2cm dilated, you feel miserable. But actually, if your cervix is fully effaced and 2cm dilated, that's good. If your baby's head is also getting lower in your pelvis, that's another good sign.
There are more things in play in early labour than the number of cm. you've dilated, so though you feel that nothing much is happening, your midwife will think differently.
When you go for a sweep, if the cervix is long, hard and closed, the sweep is impossible, and that's called an unfavourable cervix.
When women have had a lot of babies, the cervix can be 8cm dilated and not fully effaced.