Did you grow up with cousins? Your 1st cousins share your grandparents – either your father’s or your mother’s parents. Children of your aunts and uncles.
2nd cousins (technically speaking) share great-grandparents, so my children are 2nd cousins to my 1st cousin’s children.
Again, technically, my 1st cousins children are my 1st cousins once removed (meaning one generation removed from being 1st cousins)
Sometimes we loosely call those who are cousins but not 1st cousins, 2nd cousins (meaning less closely related than 1st cousins.)
Cousin has become a general purpose term for “we are related” meaning we share a common ancestor. If we all descend from Adam and Eve, the we truly are all cousins.
If you want to know the technical connection see: Cousin Chart—Family Relationships Explained