In the South, we are all just "cousin".
And in Korea, you refer to your cousins as big/little brother or sister.
Just in case the excellent descriptions/explanations don't work for your own brain, an example.
My mom, Judy, had a sister Sylvia. So write them one after another on a line.
Judy had Molly (me), and Sylvia had Mandy. Molly and Mandy are first cousins. They are written on a line together, but below their moms.
Mandy had a child first, Evan. Molly and Evan are cousins once removed. If you're writing it all out on a chart, with each "generation" on its own line, you have to make a diagonal to connect Molly and Evan.
Then Molly had Eamon. So Eamon and Mandy are, again, cousins once removed, b/c it's a diagonal to connect them.
But Eamon and Evan, THEY are second cousins, because they are two down from the sisters, but on the same line.
I never understood it until my cousin (old enough to be my father, b/c of the age difference between his father and my father) wrote it all out for me on a piece of paper while we were at a reunion. The visual made it much easier.