Here's an honest question about family: What are the children of your first cousin called?

According to Google: First cousins are non-siblings that share grandparents. Second cousins are non-siblings that share great-grandparents. Third cousins are non-siblings that share great-great-grandparents and so on.
I'm curious about it. Cause were I'm from. First cousins are basically treated the same as siblings, and their children would call me Uncle. As I would call them Niece and Nephew. It's kind of confusing.