External VS Internal dilation??

Kelsey • Happily married•Mommy to a sweet princess and 2 boys• One on the way•

Hey! I am 36 weeks pregnant today (with my 3rd child). I had an appt with my OBGYN. She checked me for dilation and told me I was dilated 1cm externally but still closed internally.

I personally had no idea that was a thing. Does anyone know what that means? I’ve tried Google, but I have not succeeded in finding an answer.