Tafsir (interpretation of Quran) is the science of interpreting and rendering commentary on the Quran, its exegesis. The sources of commentary on Islam are: 1) the Quran itself because a verse of the Quran is often used to explain another verse; 2) the Hadith. Many of the collections listed above have sections devoted to tafsir; 3) accounts of Sahabah, the companions of the Prophet Muhammad; 4) accounts of Taibun, the generation that had direct contact with the Sahabah. A few of the prominent Tafsirs are listed below. A search in a library catalog for Tafsir will yield many others.
Fiqh is the process of deducing and applying Shariah principles. Fiqh is also the collective body of laws deduced from Shariah. Ijtihad (literally striving or exertion) is the process of making a legal decision by independent or original interpretation of the legal sources, the Quran and the Sunnah. Ijtihad is embodied in the works of jurists of various schools of thought. Fiqh and ijtihad are not to be equated with divine revelation and, therefore, they are considered secondary to Quran and Sunnah. There are several methodologies of fiqh, listed below, recognized by Islamic jurists and ijtihad occurs in a variety of forms. A subject search in a library catalog for fiqh, Islamic jurisprudence, Islamic law will yield many general collections. More specific sources discussing the methodologies below can be found by searching these terms: ijma, qiyas, istihsan, istihab, urf.
The nineteen schools of fiqh madhhabs that developed during the first four centuries of Islam has condensed to five, of which four are sunni and one shia. The sunni schools are: Hanafi, Maliki, Shafi'I, and Hanbali, and the shia school is Jafari.