There are many important words used by Christians that 
mean different things to Mormons. Known as the mind control technique loaded language, it has the two-fold effect of hiding the true beliefs of Mormons from Christians they talk to, and keeping what Christians say to Mormons from having as much impact.
Mormons get all the basic tenets of Christianity wrong. See CARM's Mormon Beliefs. Since they try to appear Christian this qualifies them as a cult of Christianity. Also see CARM's A Comparison Between Christian Doctrine and Mormon Doctrine.
Mormons believe Jesus Christ is a created being, the brother of Satan and all the demons. They also believe Jesus was a polygamist with three wives. Mormons teach that Jesus Christ atoned for our sins primarily in the Garden of Gethemane, not on the cross. Mormonism and the atonement of Jesus.
Mormons believe we are not saved by grace alone. What is Mormonism’s view on the doctrine of grace?
Mormons believe that God is just an exalted man from another planet, and that we can become
gods ourselves, populating our own planet in the same way that God did
with this planet. It follows that if God was once just a man, he could have been a sinner.
Because they think that God the Father has a physical body, they believe
the Trinity is a pagan idea. However, they may quote references to make Christians think they do believe in the Trinity. If they do this they will not say they are referring to three separate gods. Jehovah is Elohim.
Mormons deny the virgin birth – they
believe God the Father had physical sex with Mary (who was also his spirit child). They also believe God the Father has a goddess wife (not Mary).
Women are to be pregnant for eternity populating their planet and can
only be saved after death if they are called from the grave by their
husband.
The believe that the biblical idea of Hell is only for apostate (fallen
away) Mormons.
They believe the Book of Mormon has its own familiar
spirit. (See Leviticus 19:31 and 20:9 & 27, Deuteronomy 18:9-12,
Isaiah 29:4, Galations 6:19-21 and others.)
Mormons have four holy books:
1. The Bible, but Mormons officially believe it only as far as they think it has
been translated correctly.
This means it takes a subordinate position to their three other holy books, so whenever the Bible disagrees with Mormon theology, the Bible is disregarded. See Mormonism and the Corruption of the Bible for more details.
2. Book of Mormon. Claimed to be another testament of Jesus Christ,
it supposedly "... contains, as does the Bible, the fullness of
the everlasting gospel."
The Book of Mormon has undergone about 4000 word and doctrine changes
since the 1830 edition. Absolutely no archeological evidence for the
Book of Mormon has been discovered (except for the part that was copied
straight from the King James Bible). See Some of the Many Changes in the Book of Mormon for some examples.
The Book of Mormon also has historical errors and contradicts Mormon theology. See Problems with the Book of Mormon.
3. Doctrines and Covenants. "Compilation of alleged divine revelations
given to the Mormon church."
There have been over 2800 additions, deletions, and word changes
since 1833. It also teaches polygamy.
4. Pearl of Great Price. Contains five sections including Selections from the Book of Moses (which itself includes the Book of Enoch) and the Book of Abraham.
There have been over 1600 word changes since 1851. Includes racism.
Mormons also believe "In addition to these four books of scripture,
the inspired words of our living prophets become scripture to us."
