Poorter is a dutch historical term for a type of Dutch or Flemish burgher who had acquired the right to live within the city gates of a city, and also had city rights. This poorterrecht or citizenship could be gained by registering with the magistrate of the city.
To receive citizen rights, a sum of money was to be paid, to prove that you weren't poor and could maintain a household. There also were religious restrictions, and numerous cities forbade Jews from attaining citizenship until the French Revolution. An oath was also taken. Some cities also had grootburgers (literally: great burghers), who received more rights then normal citizens, but had to pay a higher price to acquire it.
The city was surrounded by a city wall and a moat, and this way offered safety and protection to a certain level to its citizens. At nightfall, the city gates would be closed by the gate watch. The Keys to the city were handed to the Burgemeester, and collected again the next day.
The entire citizenry of a city was sometimes called the Poorterij (literally: Portery).