At a port of entry into Canada, 接待你的第一个官员是海关官员 (NO 边检 in Canada), 负责查你的护照和签证. If the officer sees it as necessary, you will be sent to 移民局 for an interview or a few questions. The officer will also decide if you need to go through customs for an inspection of the things you bring into the country.
Those for landing or transit to another country usually are sent to 移民局 for interviews or questions.
Most探亲 visitors, 不需要进移民局, but some may be asked to.