sunni and shi'i
One question I hear fairly often, both from my Ismaili and other-Muslim friends is: what's the difference between Sunni and Shi'i Muslims. While there are many historical, religious, and political nuances between the factions, I've compiled a quick and dirty list of some differences.
Both "Sunni" and "Shi'i" are words to describe where each group gets its guidance.
The word "Sunni" is the adjective form of the noun "Sunnah". In Arabic, adding the morpheme /i/ to the end of a word can make it into an adjective. For example, take the noun "Iraq" and add /i/ to the end; you get "Iraqi", an adjective to describe people and things from Iraq
The word "Shi'i" (plural "Shia") comes from the phrase "Shi'at 'Ali", meaning "followers of 'Ali". "Shi'at" refers to a group of people who come together with a shared belief, in this case: believing that 'Ali (the cousin/son-in-law of the Prophet Muhammad) is Muhammad's rightful successor.
The major difference between Sunnis and Shia is where they get their guidance from. These are the kinds of spiritual and material lessons that help Muslims throughout their daily lives.
As the name implies, Sunnis get their guidance from the Sunnah: a collection of teachings, sayings, and actions of the Prophet Muhammad. According to Muslims, the Prophet lived a perfect life, so emulating his lifestyle is a pious act. This is in addition to the Quran, which is believed to be the perfect text and is universally applicable.
As the "Followers of 'Ali", Shia Muslims obey the commands of 'Ali, who was appointed by the Prophet to be his successor, as well as 'Ali's descendants who are all considered to be "People of the House" of the Prophet. These descendants carry on the tradition of contextualising God's message to the current time.
While Imams exist in both Sunni and Shi'i Islam, their roles are very different.
In Sunni Islam, the imam often serves as a community leader. They lead the congregation and provide spiritual support for their followers. Each mosque has at least one imam that serves in varying capacities. The title "imam" can also refer to scholars of Islamic belief-systems and law. Sometimes a female imam may lead a female-only congregation.
In Shi'i Islam, there is only one centralised Imam at any given time. The Imam is one of the descendants of 'Ali and provides spiritual guidance to the whole community. The largest groups of Shia believe the Imam is hiding until the Day of Judgement, while smaller groups, including Ismailis, have a prominent, public Imam. All of these Imams claim to be descendants from 'Ali.
While the Quran is a fundamental factor in Islam, what it is and how it's treated can vary between Sunni and Shi'i.
According to the Sunni tradition: the Quran, in addition to being the word of God, is without fault and should be obeyed in its entirety. Any interpretation by humans of the Quran is seen to devalue its message.
In Shi'i Islam, the Quran is a contextual element. It's still considered to be the word of God by some groups, but it mostly only applies for the time when it was revealed. It's the duty of the Imams to interpret the underlying message of the Quran for changing times.
While Sunni and Shi'i prayers have a fair bit of overlap (including supplication, prostration, and certain chapters from the Quran), there are a few major differences.
Sunnis pray 5 times per day, as per the practices of the Prophet. Sunnis perform "salah" ("namaaz" in Persian), which is a form of worship that glorifies God. It features lots of takbir (saying: "God is Great") and other praises.
While many Shia pray 5 times a day, some observe that only 3 prayer times are represented in the Quran. Shia perform "du'a" which is a form of prayer that emphasises invocation. It features lots of supplication and is punctuated with prostration. Click here to read an analysis of the Ismaili Du'a.