VHEMT (pronounced "vehement"), the Voluntary Human Extinction Movement, is not an organization but rather a social, idealogical, anthropological philosophy. Those who decide to Volunteer for the Movement believe that the human species has overstayed its welcome on Earth, and agree not to add to the population. There are also the Supporters who agree we need a reduction in the number of humans, although maybe not to the extreme of complete extinction.
In general, those who are VHEMT are conscientious, compassionate, opinionated, and kind. They are also passionate about their beliefs, and quite a few even have children. They have just decided not to have any more, and to encourage others to make equally responsible decisions with their fertility.
It is the belief of most that are VHEMT that, given the state of the planet and our species, in all objectivity, bringing more of us into existence is a very unwise thing to do.