It is an institution in which interpersonal relationships, usually intimate and sexual, are acknowledged by a variety of ways, depending on the culture or demographic. This union may also be called matrimony, while the ceremony that marks its beginning is usually called a wedding and the married status created is sometimes called wedlock.

People marry for many reasons, but usually one or more of the following: legal, social, emotional, and economical; the legal establishment of a nuclear family unit; the legal protection of children; public declaration of love.

Source: Wikipedia