Shariah is the body of Islamic law. The term means “way” or “path”; it is the legal framework within which the public and some private aspects of life are regulated for those living in a legal system based on Muslim principles of jurisprudence. Shariah deals with all aspects of day-to-day life, including politics, economics, banking, business law, contract law, family, sexuality, hygiene, and social issues. There is not a strictly codified uniform set of laws pertaining to sharia. It is more like a system of devising laws, based on the Qur'an (holy book of Islam), hadith (saying of Mohammed), and centuries of debate, interpretation and precedent. Before the 19th century, legal theory was considered the domain of the traditional legal schools of thought.

Mainstream Islam distinguishes between fiqh ("understanding of details"), which refers to the inferences drawn by scholars, and shariah, which refers to the principles that lie behind the fiqh. Scholars hope that fiqh and sharia are in harmony in any given case, but they cannot be sure. Shariah has certain laws which are regarded as divinely ordained, concrete and timeless for all relevant situations (for example, the ban against drinking liquor as an intoxicant). It also has certain laws which derived from principles established by Islamic lawyers and judges (mujtahidun).
The primary sources of Islamic law are the Qur'an and Sunnah.
To this, traditional Sunni Muslims add the unanimity (ijma) of Muhammad's companions (sahaba) on certain issues, and drawing analogy from the essence of divine principles (qiyas). In situations where no concrete rules exist under the sources, law scholars use qiyas — various forms of reasoning, including by analogy. The consensus of the community or people, public interest, and others are also accepted as secondary sources where the first four primary sources allow.
Shi'a Muslims reject this approach. They strongly reject analogy (qiyas) as an easy way to innovations (bid'ah), and also reject consensus (ijma) as having any particular value in its own. During the period that the Sunni scholars developed those two tools, the Shi'a Imams were alive, and Shi'a view them as an extension of the Sunnah, so they view themselves as only deriving their laws (fiqh) from the Qur'an and Sunnah. A re-occurring theme in Shi'a jurisprudence is logic (mantiq), something Shi'a believe they mention, employ and value to a higher degree than Sunnisdo. They do not view logic as a third source for laws, rather a way to see if the derived work is compatible with the Qur'an and Sunnah.
In Imami-Shi'i law, the sources of law (usul al-fiqh) are the Qur'an, anecdotes of Muhammad's practices and those of the 12 Imams, and the intellect (aql). The practices called Sharia today, however, also have roots in local customs (al-urf).
Islamic jurisprudence is called fiqh and is divided into two parts:
• Usul al-fiqh — roots of the law: the study of the sources and methodology
• Furu' al-fiqh — branches of the law: the practical rules
The comprehensive nature of Sharia law is due to the belief that the law must provide all that is necessary for a person's spiritual and physical well-being. All possible actions of a Muslim are divided (in principle) into five categories:
• obligatory
• meritorious
• permissible
• reprehensible
• forbidden
Fundamental to the obligations of every Muslim are the Five Pillars of Islam:
• shahada (Declaration of belief in the oneness of God and in Muhammad as his final prophet).
• salat (Prayers)
• zakat (Charities)
• sawm (Fasts)
• hajj (Pilgrimage to Mecca)