DDNS vs Read-Write DNS

First Sorry for my English.

I'm Studying for the 70-640 and i have a doubt about DDNS. I undestand that Server that run dynamic updates accept registration from client but With DDNS we refers only to DNS integrated with active directory? 

Maybe because of my poor english i undestand that in the read-write DNS can be uptdated only manually?? is correct? 

Is this case we refer in primary zone not integrated with Active Directory?