Generally, it's called a wedding; but Sikhs have a sacred name for it: "Anand Karaj", which is Punjabi for "blissful union."
Sikh marital unions are closer in principle to western marriages than any other South Asian cultures, in that Sikhs are free to choose their partners, provided they are also Sikhs. However, the Anand Karaj is vastly different from a western wedding ceremony.
The Anand Karaj consists of a series of rituals, many of which involve paying respect to the Guru Granth Sahib, Sikhism's sacred text. The ceremony also does away with marriage documents, needing nothing more than an affirmation by the bride and groom of their undying love for each other.
One of the highlights of the Anand Karaj is the four wedding rounds known as the Lavan. These rounds signify the four stages in a life of love: duty to the family and community, selfless love and holy fear, freedom from any desire other than God, and total harmony. As these verses are sung, the couple walks around the Guru Granth Sahib four times.
At the end of the Anand Karaj is the feast. Unlike Christian churches, the Gurdwara, where the wedding ceremony takes place, comes with its own free kitchen where the food for the guests is prepared and served.