When talking about culture, it helps to establish the terms we are working with. Anthropologists and other social scientists define culture as a full range of learned human behavior patterns. They refer to three layers of culture -- the dominant national society, a subculture within the dominant society and cultural universals, meaning learned behaviors that are common to all cultures. For example, all cultures use some form of verbal communication, use age and gender to classify people and have rules to regulate sexual behavior.
Intra-cultural dating refers to relationships where people share the same culture, ethnicity, race and religious faith. They are people who likely have grown up in the same country, speak the same language and do not belong to belong to an ethnic subculture. These relationships are also referred to as "homogenous" -- they may be heterosexual or homosexual relationships, as long as both participants originate from the same culture. Intra-cultural relationships will not be characterized by some of the complications that can arise in inter-cultural relationships.
Inter-cultural relationships occur when two people come from different national cultures, ethnic or religious backgrounds. Inter-cultural relationships can be complicated in ways that couples from the same cultures don't experience due to the ways societies regulate the spoken and unspoken rules for intimate relationships. When people date across cultural, ethnic or religious lines, they often challenge the norms embedded in their families and the broader society. When families disapprove of the inter-cultural couple's relationship -- especially if it includes marriage -- it can lead to the dissolution of the relationship.
In the United States, there has been a long history of the social banning of inter-cultural relationships, dating back at least to the 1600s. Miscegenation laws were those that banned the marriage between white and African American or white and Native American couples and were legally in place until 1967. The Loving v. Virginia case officially lifted the legal restrictions against marriage between whites and blacks and ushered in a new age for wider social acceptance of interracial relationships. However, some studies show that the old prejudices against interracial relationships have not entirely died.