...is often a major problem when one is beginning in genealogy.
What do all the numbers mean in the expression "Fourth cousin twice removed"?
COUSIN A term formerly loosely used, and often meaning a nephew or niece.
A cousin german is a first cousin i.e. the child of an uncle or aunt. A
cousin once removed expresses the relationship between a person and his
cousin's child or parent, the 'once removed' referring to a difference
of one generation; hence 'twice removed' indicates a difference of two
generations, and so on. People who are 'second cousins' to each other are
the children of first cousins.
- from The Dictionary of Genealogy by Terrick V H FitzHugh, revised
by Susan Lumas for the Society of Genealogists
There are very many web-sites where this is explained in further detail, so I am not going to re-invent the wheel, but rather point you to some of these sites. At the time of writing, all these sites are accessable.
http://www.geocities.com/Heartland/Prairie/1956/cousin.html
http://grand_uncle_mark.home.insightbb.com/cousin.html
http://www.isn.net/~dhunter/cousin.html
http://www.jewishgen.org/infofiles/related.txt
http://www.ktb.net/~dwills/relationshipchart.htm
http://www.obliquity.com/family/misc/cousin.html
http://cswnet.com/~mgoad/cousins.htm
http://members.aol.com/coraki99/webdoc5.htm
http://statelibrary.dcr.state.nc.us/iss/gr/chart.htm