They protect Brazil's equivalent of Hogwarts, Castelobruxo. Based on the art seen on the posters, they reference the other wizarding schools like the one in Uganda - Uagadou, and the Japanese one, Mahoutokoro (the students ride to school and back on giant birds each day)
Nothing referenced in the books - all from Pottermore and we're assuming Fantastic Beasts, since she's already referenced the American school Ilvermorny in the first Fantastic Beasts film.
Edit:
Wizarding Schools - Pottermore
Yep just double-checking, it looks like each destination poster directly correlates with a location of one of the major Wizarding schools across the globe