My cousins are the children of my parent’s brothers and sisters. They are my first cousins but we just call them cousins. I have 8 first cousins.

My parents have (first) cousins and they are my first cousins once removed. If they have children their children are my second cousins.

My grandparent’s cousins are still my first cousins but twice removed. And my great grandparent’s cousins are my first cousins three times removed.

After that it gets more difficult to explain unless you look at it another way:

Cousins have the same grandparents

Second cousins have the same great grandparents

Third cousins have the same Great Great Grandparents

and so on

You are "removed" by the number of generations between you.

Wendy is a distant cousin, so is Simon. Our common ancestors are Jean and Esther Le Plastrier, my GGGGGG Grandparents.

Jean & Esther are Wendy’s and Simon's GGGG Grandparents.

Count the Gs (including the one in Grandparents)

They have FIVE Gs and I have TWO more, Simon and Wendy are my fifth cousins, twice removed!

for more see

http://en.wikipedia.org/wiki/Cousin