What is the difference between sunni, shiah and sufi muslims?

What are the differences between sunni, shiah and sufi muslims?
I am sunni and was wandering what the differences are.

http://www.spiritrestoration.org/Church/Sunni_and_Shiite_muslims.htm

Sunnis account for about 85 percent of the world's Muslims.They believe the first four caliphs,or supreme religious leaders, were the rightful successors of the Prophet Muhammed (PBUH) but have chosen subsequent leaders based on Islamic political realities of the time.

Shiite Muslims Account for about 15 percent of the world's Muslims. Shiites are dominant in Iran and are also the largest sect in Iraq. Pockets of Shiite Islam also exist in Afghanistan, Pakistan and Tajikistan. Shiites insist that true leaders of Islam must be descendants of Ali, the fourth caliph and Muhammed's son in-law. Shiism, originally a dissident faction, has its own distinct rituals and a
more organized and hierarchical clerical system than Sunni Islam.

Sufism are spiritual Muslims. They can be sunni or shiite.

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