The galaxies of the Local Group are our closest neighbors in the Universe. Because most of them are nearer than one megaparsec (Mpc) they are easily resolved into stars. This enables one to study these objects in much more detail than is possible for more distant galaxies. The members of the Local Group are therefore the laboratories in which individual objects, such as star clusters, planetary nebulae, supernova remnants, etc., can be studied in detail. Furthermore, important empirical laws, such as the Cepheid period–luminosity relation (Leavitt 1907), the maximum magnitude versus rate-of-decline relation for novae, and the luminosity distribution of globular clusters, can be calibrated in Local Group galaxies. For an earlier review of the properties of some of these galaxies the reader is referred to the proceedings of the symposium on The Local Group: Comparative and Global Properties (Layden, Smith & Storm 1994). Reviews of more recent work are provided in New Views of the Magellanic Clouds = IAU Symposium No. 190 (Chu, Hesser & Suntzeff 1999), in The Stellar Content of the Local Group of Galaxies = IAU Symposium No. 192 (Whitelock & Cannon 1999), and in Stellar Astrophysics for the Local Group (Aparicio, Herrero & Sánchez 1998).

Is the Local Group typical?

Inspection of the Palomar Sky Survey (Minkowski & Abell 1963) shows (van den Bergh 1962) that only a small fraction of all galaxies are isolated objects or members of rich clusters. The majority of galaxies in nearby regions of the Universe are seen to be located in small groups and clusters resembling the Local Group.