What is the difference between the promoter and the advisor?
As far as I understand, in the Netherlands, only full professors may be appointed "promoter", i.e. the official advisor, the super-boss if you will. Other faculty members must apparently get authorization from the university (see comment).

So if you are going to be supervised by someone who is not full professor (e.g. associate/assistant professor), that person will be appointed as "(co)advisor", while a full professor will be acting as an official advisor/promoter and will chair the doctoral examination committee.