The type, functions, and characteristics of marriage vary from culture to culture, and can change over time. In general there are two types: civil marriage and religious marriage, and typically marriages employ a combination of both (religious marriages must often be licensed and recognized by the state, and conversely civil marriages, while not sanctioned under religious law, are nevertheless respected). Marriages between people of differing religions are called interfaith marriages, while marital conversion, a more controversial concept than interfaith marriage, refers to the religious conversion of one partner to the other's religion for sake of satisfying a religious requirement.

In the Americas and Europe, in the 21st century, legally recognized marriages are formally presumed to be monogamous (although some pockets of society accept polygamy socially, if not legally, and some couples choose to enter into open marriages). In these countries, divorce is relatively simple and socially accepted. In the West, the prevailing view toward marriage today is that it is based on a legal covenant recognizing emotional attachment between the partners and entered into voluntarily.

In the West, marriage has evolved from a life-time covenant that can only be broken by fault or death to a contract that can be broken by either party at will. Other shifts in Western marriage since World War I include:

Outside the West, same-race marriage was illegal in Paraguay before becoming legal.

Key facts concerning the marriage law in Africa and Asia:

Some societies permit polygamy, in which a man could have multiple wives; even in such societies however, most men have only one. In such societies, having multiple wives is generally considered a sign of wealth and power. The status of multiple wives has varied from one society to another.

In Imperial China, formal marriage was sanctioned only between a man and a woman, although among the upper classes, the primary wife was an arranged marriage with an elaborate formal ceremony while concubines could be taken on later with minimal ceremony. Since the rise of communism, only strictly monogamous marital relationships are permitted, although divorce is a relatively simple process.

Polyandry (a woman having multiple husbands) occurs very rarely in a few isolated tribal societies. These societies include some bands of the Canadian Inuit,^{[citation needed]} although the practice has declined sharply in the 20th century due to their conversion from tribal religion to Christianity by Moravian missionaries. Additionally, the Spartans were notable for practicing polyandry.