A national identity number (birth number) is an ID number for you who have a residence permit and are going to live in Norway for more than six months.
A D number is a temporary identification number that you get if you have applied for protection (asylum), or if you have a residence permit and are going to stay in Norway for less than six months.
A FH number is used in health care to uniquely identify patients that does not have a known national ID or D number. A FH number does not have any information about age or gender.
A H number is a number used for assistance, a unique identification of a person that does not have a national ID or a D number or in cases where this is not known. A H number contains information about age and gender.
In Norway there are several different ID numbers