Islam has a clearly delineated cosmos in which both the territories and the inhabitants are clearly set out. In the present age, there are the [heavens] and the [earth], which were created by and are now ruled over by Allah. The angels are Allah's messengers from heaven to the earthly realm, where the humans, the animals, the [jinn], and the [shaitans] ("satans"=demons) exist. In the future, however, the heavens and the earth will be transformed into paradise and hell. This will happen at the [Judgement Day], when all the dead will be [resurrected], judged, and then either rewarded with eternal life in [paradise] or with eternal punishment in [hell]. So Allah's creation has movement; what appears as a steady state to humanity is actually a progression towards Judgement Day and Allah's transformation of the cosmos into a new creation.
The inhabitants of these realms of the cosmos can be systematically described by a limited number of principles. The first of these is the opposition between light and darkness (the absence of light), the second is the opposition between good and evil (rebellion against Allah), and the third is presence of the divine, life-giving spirit.
In Islam, Allah is the sole god; there is no god other than Allah. He is singular and unified, with no divisions. He has and will eternally exist. Allah is the embodiment of both light and goodness. Most importantly, he is uncreated light--light that has existed forever as Allah. All other light, by contrast, was created by Allah. Allah has many roles in relationship to his creation, but perhaps two are the most important. First, he is the object of submission by humans (i.e., Moslems). Second, he is the Merciful Judge, who on Judgement Day will decide the fate of all aspects of his creation, most importantly, all humans. Furthermore, Allah is the epitome of all good things: knowledge, wisdom, truth, beauty, and so on.
The angels are like Allah in that they too are light. Or, to be slightly more specific, angels' bodies are light. However, they differ from Allah in that they are his creations and that their light is thus created light. These bodies of light come to life when they are combined with a spirit. Indeed, the spirit is life itself. Since the spirit comes from Allah (he blows his spirit into new bodies, living things have a share in Allah's nature. Because both aspects of the angels' nature--their body of light and their spirit--come from Allah, they are creations that are completely made of Allah's nature. They are totally good and cannot rebel against Allah. They therefore cannot be judged. Angels live in heaven and serve as Allah's messengers to the rest of his creation.
Human beings, by contrast, are much more problematic. On the one hand, their bodies are created out of darkness. In discussions of the dark character of humanity, Islam usually speaks of humans as being made out of earth or clay. Remember, darkness is merely the absence of light; it is not evil in and of itself. While angels' bodies are made out of Allah's nature (light), therefore, humans' bodies are made out of the lack of Allah's nature (darkness). On the other hand, the humans receive Allah's spirit just like the angels. So whereas angels bring together only one nature in themselves (that of Allah), human beings combine Allah's nature (spirit) with a substance that is the lack of Allah's nature (the darkness of the body).
The combination of these two natures in humanity creates a [soul] in each individual. The soul is spirit, but spirit that has been influenced by the body's character of darkness. Human beings thus can choose whether or not to follow Allah. Following, or submitting, to Allah is good, while not following constitutes rebellion and is therefore evil. Unlike angels, then, humans can choose the course of their life. This choice is the basis for Allah's judgement of each individual on Judgement Day. It goes without saying, of course, that humans live on earth.
Finally, sharing the earthly realm with humanity, Islam identifies the jinn. In nature, the jinn stand between angels and human beings. Their bodies are fire, and fire is seen as mixture of light and darkness. Like humans, then, jinn have the ability to choose between good and evil, although they are not necessarily one or the other. Moslems often see jinn as untrustworthy, however. Jinn can be tricksters who will play practical jokes on people. Like humans, jinn will also be judged on Judgement Day.
There is one jinn worth noting in particular, The Satan, usually called [Iblis]. He is a jinn who first worshiped Allah extensively and because of his piety gained a following among other jinn. When Adam was created and given his central place in creation, Iblis was jealous and rebelled against Allah, taking his followers with him. Iblis was caste from Allah's presence and restricted to the earthly realm. His followers are now known as the shaitans, or demons.
In Islam, the human problem is seen as forgetfulness, even active forgetfulness. But forgetful of what? Islam holds that all humans are born with a pre-disposition to Islam; it is part of their innate nature. But as a baby grows up, it may be turned in another direction. This may be a turning towards another religion or perhaps away from recognition of the divine altogether. The human problem is thus the forgetting of one's inborn tendency to follow Allah.
The solution to forgetfulness, of course, is to remember. Islam holds that people need to remember Allah and his path, namely, the path of submission to him. Once they remember, they then need to submit to Allah and follow his will.
This is why Allah sent the [prophets], namely, to remind people of Allah and his message. Most of the prophets important in Islam are figures in Judaism and Christianity. Some of the most frequently mentioned are: Adam, [Abraham], Moses, Solomon and [Jesus]. These followers of Allah all brought his message, but in every case it was misunderstood, distorted, or forgotten. Thus while some of Allah's message became known, the complete message was never available to humanity.
To solve this shortcoming, Allah sent [Mohammed]. By dictating the [Quran] to him, Allah ensured that his message would be passed to humanity undistorted. Since Mohammed was the prophet who "got it right," he is the Final Prophet. Allah will make no more attempts to help humankind remember their innate link to him.
Note: I am indebted to The Vision of Islam, by Sachiko Murata and William C. Chittick (New York: Paragon House, 1994), pp. 45-132 for much of this discussion of the Islamic cosmos.