The main theoretical aspects of gravitoelectromagnetism ("GEM") are
presented. Two basic approaches to this subject are described and the role of
the gravitational Larmor theorem is emphasized. Some of the consequences of GEM
are briefly mentioned.Comment: 15 pages, no figures; v2: slightly improved version published as the
third chapter of The Measurement of Gravitomagnetism: A Challenging
Enterprise, edited by L. Iorio (Nova Science, New York, 2007), pp. 29-3
