Final answer:
Cultural practice of marrying outside one's group is called exogamy, where marriage is based on love and compatibility, differing from endogamy which is marriage within one's own social group.
Step-by-step explanation:
The cultural practice of marrying outside of one's own group is termed exogamy. Exogamous marriage refers to the union of spouses from different social categories, such as different racial, ethnic, or social class backgrounds. Despite the existence of social norms that may encourage endogamy, or marrying within one's group, emphasis on values like love and compatibility has led to an increase in exogamous marriages. This contrasts with endogamy, where individuals choose partners within their own class or social group. This is a significant aspect of cultural anthropology, which studies societal norms and customs related to familial structures and marriage.