A resident is someone who lives somewhere particular, or a doctor-in-training who takes care of the patients at a hospital under the supervision of other doctors.
You are a resident of wherever you live — your house, town, planet. (Let's assume we're all residents of Earth.) It's where you were born or where you've lived for awhile. Doctors who have their medical licenses but need more training become residents of hospitals. Animals that don't migrate are residents, too. Although it's usually a noun, it can be an adjective, like in the horror movie no one wants to live in, "Resident Evil."