1. Sunni and Shi'i Islam
The division arose over the question of who has authority to rule over the community of Muslims (Ummah).
Most practices have remained the same for both groups.
They both share the same prophetic revelatory event described in the Qur'an and the Sunnah.
They both accept as fundamental Allah's unity and the mission and message of Muhammad.
Differences developed into a philosophical dispute over the nature of the Imam.

2. should be chosen through consensus of the ummah
Shi'i
Sunni
must be a descendent of Ali
should be chosen through consensus of the ummah
spiritual leaders
belief that Imams have always been around since the time of Adam with Adam being the first Imam
to lead the Islamic world both spiritually and in secular matters
belief in the eventual return of the 12th Imam - called the Mahdi who will lead the forces of good against evil in an apocalyptic battle before the Day of Judgement

3. There are many different branches of both Sunni and Shi'a Islam
There are many different branches of both Sunni and Shi'a Islam. Below are some of the better known groups.
Sunni Tradition
Khariji'i
arose 7th Century CE
belief in absolute purity of conduct and belief
exists today in small groups in North Africa and southern Arabia
Muwahhidun
(Wahhabis)
arose around 1800
adhere to the teachings of Ibn Taimiya condemning all innovations in Islam
Mu'tazila

4. Shi’a Tradition The Imami (twelvers) Ismaili (Seveners)
dominant branch of Shi'a
believe the 12th Imam after Ali is now hidden
Ismaili (Seveners)
The Alawite of Syria
The Druze
Zaidi