Goblins are everywhere, much like humans, but they are native to Belanna.
They are not very adventurous, but they can overpopulate an area quite fast forcing some of them to either migrate or die. It's a 50/50 most of the times.
They mainly stay on the continent they are from, and if they move from there, it's mostly by accident or force.
Sexual Dimorphism
Goblins have no assigned gender, and can, when needed and desired, choose their own gender, and both have the possibility to carry out the pregnancy.
The difference between the genders, however, is in "input or output" alone.