Also called Nikah mut‘ah is a temporary marriage license, and a practice supposedly dating back to when the Prophet Muhammad was creating short term alliances. The male in the relationship has to pay a fee too his temporary fee, and set a pre determined amount of time for how long the marriage will go on for (this can range anywhere from hours to years.) After the marriage ends the woman must wait 2 menstrual periods before marrying again.
Because Auditory in Iran can led to being lashed or even executed, temporary marriage has become a common practice among those looking to have sex, but not looking to be forever married. It is commonly practiced in Shia communities.