Tawhid and the nature of god
Tawhid (the Arabic word for "individuality" or "wholeness") is a fundamental concept in the Islamic religion. In fact, this concept is what set aside Islam at its creation from the other numerous and various religions that surrounded the Arabian peninsula, the birthplace of Islam. The concept refers to Islamic monotheism, and the belief in one god: "Allah", the Arabic word for "the God".
Tawhid, referring to the idea of the wholeness and all-encompassing nature of Allah, is therefore a fundamental aspect of the religion. Not only does it confirm the monotheist nature of Islam, but also allows the religion to place Allah above all else: indeed, Allah is referred to in the Qur'an by various terms used to reinforce the supremacy of God, including "Kings of all kings" (al-Maleek al-Maloukiyah), to show that Allah is in fact not a God amongst other Gods, but the unifying God of Islam, the one which directs the followers of the faith in their conduct. Not only do the implications of Tawhid assure Islamic monotheism, but also shared conduct, in the path of Allah.


Akhirah and the afterlife
Akhirah (the Arabic word for "afterlife") is a semi-integral part of Islamic theocracy that touches on the subject of the afterlife and existence after death. It ties into the Islamic theory of Jannah  and Jahannam, or heaven and hell.
Akhirah is referenced heavily in Islamic Theory pertaining to judgment day (Yaum al-Qiyamah), where the souls of the departed are judged by Allah in tradition Judeo-Christian-Islamic fashion. Rather than being a duty for Muslims, it is simply an eventuality that dictates the follower's conduct during his life, for much like in the Christian or Jewish religions to which it is related to, Islamic theocracy assures its followers that their actions will contribute to the decision of Allah when he chooses where the judged will depart to in his afterlife: either to Jannah, the heaven, or to Jahannam, the hell.