Marriage is the institution of legally joining two or more persons, though in most Western countries it is now limited to just two people. This comes with a variety of benefits, varying from financial stability, to insurance sharing, to a feeling of personal unity. Marriage redefines who your next of kin are in many countries conveys advantages in tax and inheritance law. Religion often plays a role, though non-religious weddings are not unheard of.
In many countries, particularly Islamic ones, Polygamous marriages of two or more wives and one husband are allowed (Islamic law limits a man to no more than four wives at a time). Polygamous societies are almost invariably Patriarchal and have a poor record on Women's rights - not least because the disequilibrium of polygamy in a society with even numbers of men and women tends to result in women and girls being married of at a relatively young age.
That's the only time in their lives when traditional, practising Christians are allowed to choose who they have sex with and afterwards if the relationship doesn't work out the couple are stuck with their choice. Divorce is discouraged in some Sects and denominations and forbidden outright in others. That's called the happy event!
Same sex marriage
In recent years, same sex marriage has been a subject of controversy regarding homosexuals. To the sane mind, it is apparent that a same sex couple being joined in matrimony has absolutely no effect on anyone else, anywhere. However, in some countries such as the US conservatives have taken it upon themselves to thwart the "unholy unions", as dictated by their interpretation of the Bible. Preceding this on the right wing agenda, is the subjugation of blacks, and that of women, also by the same "holy decree". When questioned on the matter, any Conservative will say that their definition of marriage, is that of a man and a woman. It is apparent that the Republican Party is much more concerned over the perceived definition of a word, than the freedoms of their fellow Americans. By that logic, anyone who is "conservative" is also stingy, selfish, and afraid of change. This is unacceptable, because unlike sexuality, political affiliation is a choice.