A great part of the teachings in Islam are about the actions of every Muslim. These duties which are called practical rulings are discussed in a science called fiqh. The original source for knowing these duties is the Qur'an and tradition (speeches and acts of the Infallible Ones (a)). In general, practical duties of every Muslim can be categorized in three fields of worship, ethics, and society (transactions).
Acts of Worship
Worship is an act to be practiced with the intention of obeying the order of God. Acts of worship are either obligatory or recommended. The most important obligatory act of worship in Islam is daily prayers. Some of the most important obligatory acts of worship are: fasting in the month of Ramadan, zakat, khums, hajj, and jihad.
There are many teachings regarding moral actions in original sources of Islam (the Qur'an and tradition of the Infallible Ones (a)). Introducing good and bad morals and practical ways to achieve moral perfections, advising about observation of people's rights and orders for regulation of social and family relations are among moral teachings in Islam.
Civil and Social Duties
In Islam, there are many rulings for many daily affairs; such as marriage, divorce, buying and selling, lease, mortgage, foods and drinks, hunting, criminal issues and judgement. These rulings are discussed in the science of fiqh under the title of transactions.
Today, Muslims are in two big branches of Shi'a and Sunni; each of which has several sects. The most important differences between Shia and Sunni is over the issue of Imamate or caliphate of the Prophet (a). This disagreement emerged the first days after the demise of the Prophet (a) among his Companions.The differences between the two schools of thought are not reduced in Imamate, as they also have differences in beliefs and practical rulings. Other differences of views between the two schools are their views toward the justice of the Companions of the Prophet (s), infallibility of Prophets (a), determination and free will, some rulings of wudu, daily prayers, and hajj and different views about temporary marriage.
Shi'a is one of the two major schools in Islam which has several branches. The common factor among all these sects is the belief in the Imamate and caliphate of Imam Ali (a) and his two sons, Imam al-Hasan (a) and Imam al-Husayn (a) after the Prophet (a).Shi'a live in most Islamic countries, but most of their population is in Iran, Iraq, Azerbaijan, Pakistan, and Lebanon.
Regarding population, Sunnis are more than Shi'a. Followers of this school have different branches as well; the divisions of which are based on two issues of fiqh and beliefs. Their differences in beliefs led to three schools of Mu'tazila, Ash'ari, and Maturidi; and their differences in rulings and secondary principles of religion led to formation of four schools of Hanafi, Maliki, Shafi'i, and Hanbali in fiqh.