This doesn't affect the Raspbian versions of Debian, just the standard x86 versions you download from the Debian site.
When installing Debian, you end up with the root user, and the user you have to create during the installation. The root user works great from the command line when you are sat at the computer, but I think that SSH for this user is disabled by default, as you can't login as root remotely.
You can remote using your primary user, but this user cannnot do anything that requires super user rights (because by default, this user is not part of the SUDOers group).
Using SUDO command doesn't work either (unlike raspbian) but you can simply elevate yourself by using:
SU root_user_password example SU bubbles (if bubbles is the root users password)
Now you can perform all tasks requiring SUDO rights.