Fixed-Term/Temporary Marriage are different names for the Arabic word of 'Mut’ah' is a contract between a man and woman, much in the same way the Long-Term/Permanent/Conventional marriage is.

One misconception regarding temporary marriage is that some people think that the woman engaged in temporary marriage can have contract every other hour. This is completely misrepresentation of temporary marriage. After such contract has been expired, the woman has to wait for two months (Iddah) before which she can not marry any one else.
"...Except the forbidden women) the rest are lawful unto you to seek them with gifts from your property (i.e., dowry), provided that you desire protection (from sin), not fornication. So for whatever you have had of pleasure (Istamta’tum) with them by the contract, give unto them their appointed wages as a duty. And there is no sin for you in what you both agree (in extending the contract) after fulfilling the (first) duty. Lo! Allah is ever Knower, Wise." (Quran 4:24)
Fixed-Term/Temporary Marriage are different names for the Arabic word of "Mut’a” (sometimes pejoratively translated as Pleasure Marriage) which is a contract between a man and woman, much in the same way the Long-Term/Permanent/Conventional Marriage is. The main difference is that the temporary marriage longs only for a specified period of time, and man and woman will become stranger to each other after the expiration date without divorce.
One misconception regarding temporary marriage is that some people think that the woman engaged in temporary marriage can have contract every other hour. This is completely misrepresentation of temporary marriage. After such contract has been expired, the woman has to wait for two months (Iddah) before which she can not marry any one else. This issue, among others, will be discussed later in detail.
The first one who legislated Mut’a with all the rules pertaining to it, was the Messenger of Allah (S), after it was revealed in Qur’an. All Muslims agree that the Messenger of Allah legislated Mut’a and made it legal after his migration to Medina, and the Muslims practiced it during his lifetime. (see al-Mughni, by Ibn Qudamah, v6, p644, 3rd Edition).
However there is a disagreement between the Shi’a and most of the Sunnis concerning whether the Prophet later banned it or not. Most Sunnis assert that although the Prophet legislated it, he later forbade it. This is while the Shi’a believe that temporary marriage was never abandoned by the Prophet (S). Allah revealed it in Qur’an, and it was being widely practiced to the end of his lifetime and during the period of Abu Bakr and the early days of Umar’s rule, until Umar forbade it.
In Parts I through IV, we study the verse of Mut’a marriage in Qur’an and look into the Sunni commentary (Tafsir) of this verse, and review the traditions reported in the six authentic Sunni collections about Mut’a. In Part V we discuss the purposes of marriage as well as the chronological orders of the prohibition of illegal sex and the permission of Mut’a in the history of Islam. In Part VI the similarities and differences which exist between the two types of marriage are presented in detail. In Part VII we discuss the necessities and the advantages of the temporary marriage, and finally in Part VIII we answer some frequently asked questions regarding to the Mut’a.