Dilation is the hole opening up, thinning is from top to bottom thinning out. I am explaining badly. Google Image search effacement(thinning) and dilation. There are pictures.
Yeah, I'm 100% thinned and only 1cm dilated. They tried to explain it to me, but I'm still confused. I know that dilating means your cervix is opening for the baby to push through, hyt the thinning still confuses me