Biological genders are male, female, and intersex. These are based on the DNA of the individual.
Social genders often corresponds to biological genders, but is discovered as the individual grows from infant to child to adult and may change over time, and by self identification.
Biological gender is similar to vital statistics, such as birth date and place.
Social gender is similar to occupations or religions.
Both these genders are important, but the biological gender is typically of more interest in genealogy because lineage linked genealogy is based on biological relationships. Because we also care about adoptive relationships because of the significance of both nature and nurture in human development, social gender is also interesting.
Both types of gender are important but social gender should never be confused with or replace the biological gender.