The Fundamentalist Church of Jesus Christ of Latter Day Saints has more than a century of history and a system of beliefs and practices that have long set it apart. Here's a look at its roots and beliefs:

Q: Is the FLDS Mormon?

A: Members say they represent the only true Mormon church — a claim otherwise rejected by people who consider themselves Mormon. As Mormon historian Martha Sontag Bradley of the University of Utah puts it: ''The FLDS is as foreign to contemporary Mormons as they are to outsiders.''

Q: What is the connection between the FLDS and the mainstream Mormon church — the Church of Jesus Christ of Latter-day Saints?

A: Both churches trace their origins to Joseph Smith. They believe that in 1823, an angel visited Mr. Smith, son of a farmer in upstate New York, and told him to reboot authentic Christianity, which was lost shortly after the deaths of the original apostles.

Among the teachings: Israelites came to what is now America more than 2,600 years ago, and their descendents were visited by Jesus after his resurrection. Both churches also believe that God was once a mortal man. The LDS church has more sacred texts than the Bible, including the Book of Mormon.

And the president of the church is considered a prophet, no less than Elijah, through whom God can deliver new revelations.

Q: Where did the FLDS come from?

A: The FLDS, formally incorporated in 1991, is one of the largest splinter groups that rejected new Mormon revelations.

One of the early tenets of the LDS church was polygamy, patterned on the Biblical patriarchs. In 1890, as Utah was trying to become a state, the Mormon president announced that polygamy was no longer acceptable. But the FLDS believes that a former head of the LDS church instructed a group of Mormons to continue plural marriages.

A second major revelation occurred in 1978. Until that time, black men were not allowed full membership — ''priesthood'' — in the LDS church. The FLDS also rejects that change.

Q: Are there differences in how the churches are organized?

A: The LDS president is closely advised, as a matter of church doctrine, by a group of more than a dozen other men. The organization that became the FLDS started with a group of advisers. But the father of Warren Jeffs, the current prophet, declared in the 1980s that the leadership should be held by one man.

Q: Does the FLDS president hold powers that the LDS president does not?

A: One important power is the ''placement marriage,'' according to historian Marriane T. Watson. Mr. Jeffs has the right and responsibility to assign girls or women to their husbands.

Q: Are there other differences between the FLDS and LDS?

A: The LDS church once taught that its members should be self-sufficient and greatly restrict contact with nonmembers. The FLDS still holds those teachings, as shown by the substantial Eldorado, Texas, compound. The compound might also represent a location for a ''gathering of the saints'' to precede the return of Jesus. LDS teaching no longer emphasizes the need for a literal, physical gathering place.