Take a look here: http://www.hinduwebsite.com/brahmanmain.asp
This single, unitary divinity had several aspects and names in the Upanishads, two of the most important are Atman, "Universal Spirit," and Brahman. The word "brahman" in Sanskrit originally meant "power" and specifically referred to the power of prayer or sacrifice to bring about material change in the world (hence the word brahmin for priest); so that Brahman seems to refer to the power that brings about and changes the physical universe. In the Upanishads , Brahman is not only the principle and creator of all there is, but is also the sum totality of the universe and its phenomena.
This dual nature of the single divinity or totality of the universe, Brahman and Atman, gets worked out in the following way. Brahman can be located both in the physical, external world and also in the spiritual and inner world where it is present as Atman, "universal spirit." Now every human being has an undying soul (atman) which, because of samsara, lasts through eternity from life to life; this undying atman is a microcosm of Atman, the universal spirit, which is identical to Brahman. By understanding your true Self, by coming to know one's own undying soul, one then arrives at the knowledge of Brahman itself; the key to understanding the nature of the one unitary principle of the universe is to see one's (undying) self as identical with Brahman: "aham Brahmasmi": I am Brahman.
Here's the equation: Brahman=Atman=atman. Brahman is the totality of the universe as it is present outside of you;, Atman is the totality of the universe as it is present within you; Brahman is the totality of the world known objectively, Atman is the totality of the world known subjectively. This equation fundamentally underlies the whole of Krishna's teachings concerning dharma in the Baghavad Gita .
In the later development of Hinduism, Brahman would become one aspect of a triune god and would represent the creation aspects of that god.
Classic Hinduism promotes four different goals. Like other aspects of Hinduism, the goals are split between those emphasized by the "life is good" perspective and those emphasized by the "life is bad" perspective. The three life-affirming goals are Dharma (virtue), Artha (success) and Kama (pleasure), while the life-negating goal is that of moksha (release).
The three "life is good" goals can be pursued all at once or at different times in one's life. Some goals seem more suited to different stages of life than others.
Dharma is the practice of virtue, the living of an ethical and ritually correct life. The definition of what is virtuous, however, varies, depending on a person's caste and jati membership. The primary virtue is to fulfill the duties assigned to one's caste. Thus a brahmin should offer sacrifices and do them to the best of his ability, while a Vaishya silversmith should create his plates and bowls as strong and beautiful as possible. If either person tried to do the other's job, that would be seen as violating their caste duty. The dharma a person is expected to fulfill also varies depending on their stage of life. A student, for instance, becomes virtuous through a different set of actions than a householder.
Artha is the working for and achieving of success, in terms of both wealth and power. This means it is religiously important to be a successful businessman, to sell a lot of carpets for instance, or to manage a successful restaurant. It also means that it is religiously good to serve on the city council, to be active in civic organizations, or even to become a politician. This kind of success is most easily achieved at the householder stage of life.
Kama is pleasure, usually understood as aesthetic pleasure of all kinds. This includes: the producing and enjoyment of art, music, dance, drama, literature, poetry, and sex. (The "Kama Sutra," which may be one of the best known Hindu texts in the West, is about the aesthetic pleasure of men and women; it discusses beauty, music, dance and sexual activity.) It is thus religiously praiseworthy to take part, to support, or just to appreciate any form of pleasure. This should always be done, of course, within the realm of dharma (i.e., in a virtuous manner).
The "life is bad" goal is moksha. It is the striving for release from life (since, after all, it is bad). To achieve this, a person must turn their back on life and strive to live without the things that make up life. At first, it requires the turning away from the first three goals, of rejecting family, comforts, pleasure, education, and so on. It also requires one to become an ascetic, a hermit, and to spend one's time in contemplation. This contemplation should be directed towards overcoming the maya that clouds human perception of reality and towards realizing the true nature of the cosmos and one's place in it (that atman and Brahman are one).