Maimonides explains that the institution of marriage is a Biblical innovation (MT Hilkhot Ishut 1:1). Before the Tora was given to the Jewish people, he says, a man would find a woman, bring her to his home and they would live together and bring children without any public commitment or formal ceremony. Also, since in ancient times there was no institution of marriage there was no formal process of divorce. If one of them wished to leave the family, he or she could do so at any moment.
The Tora established the Mitsva of marriage: when a man and a woman wish to live together, first, they should get married . This is learned from the Pasuq in Debarim 22:13 “When a man takes (=marries) a woman …” .
Jewish marriage is a ceremony of a public nature and therefore it requires the presence of two witnesses. It is also an accepted standard that, in normal circumstances, the wedding will be held in the presence of at least a Minyan, ten adult men.
The wedding consists of two steps: qiddushin (or irusin) and hupa (or nisuin). The first one, qiddushin is the formal and legal betrothal or engagement (not to be confused with the proposal/engagement we do today). The qiddushin is done mainly to seal the formal commitment to getting married. The qiddushin is performed by a legal process called qinyan (lit. acquisition) . The standard custom today is doing this qinyan by giving a ring to the bride. Although, in some Syrian communities, following a very ancient custom, the groom gives the bride a silver coin instead of a ring. When the groom gives the ring to the bride, he consecrates her saying: “Behold, you are consecrated to me (to be my wife ), with this ring, according to the law of Moshe and Israel”. Upon receiving the ring, the two are formally engaged. However, the couple still cannot live together. They will be considered formally married only after the Hupa.
It is very important to mention that in Talmudic and pre-Talmudic times, this first step of the wedding, or qiddushin, was celebrated usually one year before the actual wedding ceremony or Hupa took place. During that year between the qiddushin and the Hupa the couple was formally engaged but not married. They would still live each in his or her parents home. Still, the woman was considered me-orasa or formally betrothed. Thus, if the couple decided to disolve the qiddushin, the process of a formal divorce was required.
The year between the qiddushin and the hupa was consecrated to building the new house, preparing the wedding dresses, the food and everything needed for the Hupa and for the seven-days party which follows the Hupa (sheba berakhot). That year also served to strengthen and build up the relationship between the bride and the groom in the spiritual and emotional realms, in anticipation for their intimate life as husband and wife.
This year period between the qiddushin and the Hupa is not in practice anymore. In our days, the qiddushin is done under the Hupa, as part of the same ceremony. Why? There were many practical issues that demanded this change. For example, the persecutions Jews suffered in exile. Imagine if the groom had to run away to save his life. If that happened, the bride, who was now in a state of betrothed-but-not-married, will not be able to marry to someone else in the future because she needed now a GET, a formal divorce bill, from her groom. Because of this and similar circumstances, we do now the qiddushin and the Hupa at the same time.
Today, the Jewish wedding ceremony consists of the giving of the ring (qiddushin) and the Hupa. These two steps are now completely integrated, and most people would not know or realize that, formally, these are two different ceremonies.