I was trying to find an earlier similar question to which I provided and answer but cannot immediately.
This is quite easy to remember. Cousins (not removed) must be of the same generation. First cousins share common grandparents (that is, one of each of their parents are siblings). Second cousins share great-grandparents. Third cousins share great-great-grandparents and so on. In short, they higher number cousins are �wider apart� but at the same level in the family tree.
Cousins �removed� are children (or parents) of your cousins. So a first cousin once removed is a child of your first cousin. First cousins twice removed are grandchildren of your first cousins. Interestingly your first cousin�s parents are technically your first cousin once removed, but they are of course your uncle or aunt.