Visible citizens are those who are registered in the population register. For some subjective or objective reason, the invisible are not registered. 

By "visible" we mean those who are psychologically and economically stable, and by "invisible" those who live in fragile situations, hiding and isolating themselves in common life

The invisible ones can be asylum seekers, beneficiaries of reception, undocumented or homeless people, as well as people with disabilities, most often hiding and isolating themselves in the community. Among these citizens, there are also Europeans who have chosen not to register in a communal register of voters because they do not like, for example, the obligation to vote.