Genealogy is the study and tracing of family pedigrees. This involves the collection of the names of relatives, both living and deceased, and establishing the relationships among them based on primary, secondary and/or circumstantial evidence or documentation, thus building up a cohesive family tree. Genealogy is often also referred to as family history, although these terms may be used distinctly: the former being the basic study of who is related to whom; the latter involving more "fleshing out" of the lives and personal histories of the individuals involved.
GEDCOM - A common format for storing family trees offline.
Resources - Where to find lost relatives and research your family history?