The following definition of genealogy strikes me as especially well-written. It comes from the BCG website [http://www.bcgcertification.org/certification/faq.html#definition].
"Genealogy is the study of families in genetic and historical context. Within that framework, it is the study of the people who compose a family and the relationships among them. At the individual level, it is biography, because we must reconstruct each individual life in order to separate each person’s identity from that of others bearing the same name. Beyond this, many researchers also find that genealogy is a study of communities because kinship networks have long been the threads that create the fabric of each community’s social life, politics, and economy.
Good genealogists use every resource and tool available, emphasizing original records created by informants with firsthand information. Genealogists have long studied economics, geography, law, politics, religion, and society in order to properly interpret records, identify individuals and relationships correctly, and place their families in historical context. The modern field of genetics has added another valuable tool to their intellectual toolbox.
Serious genealogists do specialize, as do all professional and scholarly fields, because no one can be an authority in all aspects of any subject. Some genealogists specialize in an ethnic group, some in a geographic region, and some in a particular type of resource such as military or immigration records. Some specialize in work with the legal system, others in medical research. The advent of genetics has created yet another specialty: genealogists whose expertise lies in the interpretation of DNA results and its application to genealogical research problems."