Church of Jesus Christ of Latter-day Saints

When one refers to Mormons, they are usually refering to the Church of
Jesus Christ of Latter-day Saints.

http://lds.org/

An FAQ about their beliefs can be found here:

http://mormon.org/question/faq/category/questions/0,8789,895-1-16,00.html

Mormons are a very new Christian religious movement founded by Joseph
Smith. Most Mormons settled what is now modern day Utah. They were
known for practicing polygamy, this practice has largely been
abandoned (except by some fundamentalists).