The main forms of religious belief are:
Theism:
The belief in the existence of one or more divinities or deities, which exist within the universe and yet transcend it. These gods also in some way interact with the universe (unlike Deism), and are often considered to be omniscient, omnipotent and omnipresent. The word "theism" was first coined in the 17th Century to contrast with Atheism. Christianity, Hinduism, Islam, Judaism, Sikhism, Baha'i and Zoroastrianism are all theistic religions.
Monotheism:
The view that only one God exists. The Abrahamic faiths (Judaism, Christianity and Islam), as well as Plato's concept of God, all affirm monotheism, and this is the usual conception debated within Western Philosophy. Jews, Christians and Muslims would probably all agree that God is an eternally existent being that exists apart from space and time, who is the creator of the universe, and is omnipotent (all-powerful), omniscient (all-knowing), omnibenevolent (all-good or all-loving) and possibly omnipresent (all-present). The religions, however, differ in the details: Christians, for example, would further affirm that there are three aspects to God (the Father, the Son and the Holy Spirit).
Exclusive Monotheism: The belief that there is only one deity, and that all other claimed deities are distinct from it and false. The Abrahamic religions, and the Hindu denomination of Vaishnavism (which regards the worship of anyone other than Vishnu as incorrect) are examples of Exclusive Monotheism.
Inclusive monotheism: The belief that there is only one deity, and that all other claimed deities are just different names for it. The Hindu denomination of Smartism is an example of Inclusive Monotheism.
Substance Monotheism: The belief (found in some indigenous African religions) that the many gods are just different forms of a single underlying substance.
Pantheism:
The belief that God is equivalent to Nature or the physical universe, or that everything is of an all-encompassing immanent abstract God. The concept has been discussed as far back as the time of the philosophers of Ancient Greece, including Thales, Parmenides and Heraclitus. Baruch Spinoza also believed in a kind of naturalistic pantheism in which the universe, although unconscious and non-sentient as a whole, is a meaningful focus for mystical fulfillment.
Panentheism:
The belief (also known as Monistic Monotheism), similar to Pantheism, that the physical universe is joined to God, but stressing that God is greater than (rather than equivalent to) the universe. Thus, the one God interpenetrates every part of nature, and timelessly extends beyond as well. The universe is part of God, but not all of God. The word (which can be translated as "all in God") was coined by the German philosopher Karl Christian Friedrich Krause (1781–1832) in 1828 in an attempt to reconcile Monotheism and Pantheism.
Deism:
A form of monotheism in which it is believed that one God exists, but that this God does not intervene in the world, or interfere with human life and the laws of the universe. It posits a non-interventionist creator who permits the universe to run itself according to natural laws. Deism derives the existence and nature of God from reason and personal experience, rather than relying on revelation in sacred scriptures or the testimony of others, and can maybe best be described as a basic belief rather than as a religion in itself. The roots of Deism lie with Heraclitus and Plato, but it was also popular with the natural theologists of 17th Century France and, particularly, Britain, who rejected any special or supposedly supernatural revelation of God.
Pandeism: The belief that God preceded the universe and created it, but is now equivalent to it - a composite of Deism and Pantheism.
Panendeism is a composite of Deism and Panentheism. It holds that, while the universe is part of God, it operates according to natural mechanisms without the need for the intervention of a traditional God, somewhat similar to the Native American concept of the all- pervading Great Spirit.
Polydeism: The belief that multiple gods exist, but do not intervene with the universe - a composite of Deism and Polytheism.
Misotheism:
The belief that a God or gods exist, but that they are actually evil. The English word was coined by Thomas de Quincey in 1846. Strictly speaking, the term connotes an attitude of hatred towards the god or gods, rather than making a statement about their nature.
Dystheism:
The belief that a God or gods exist, but that they are not wholly good, or possibly even evil (as opposed to eutheism, the belief that God exists and is wholly good). Trickster gods found in polytheistic belief systems often have a dystheistic nature, and there are various examples of arguable dystheism in the Bible.
Ditheism (or Duotheism):
The belief in two equally powerful gods, often, but not always, with complementary properties and in constant opposition, such as God and Goddess in Wicca, or Good and Evil in Zoroastrianism and Manichaeism. The early mystical religion Gnosticism is another example of a ditheistic belief of sorts, due to their claim that the thing worshipped as God in this world is actually an evil impostor, but that a true benevolent deity worthy of being called "God" exists beyond this world.
Polytheism:
The belief in, or worship of, multiple gods (usually assembled in a pantheon). These gods are often seen as similar to humans (anthropomorphic) in their personality traits, but with additional individual powers, abilities, knowledge or perceptions. Hard Polytheism views the gods as being distinct and separate beings, such as in Ancient Greek Mythology. Soft Polytheism views the gods as being subsumed into a greater whole, as in most forms of Hinduism.
Henotheism: The devotion to a single god while accepting the existence of other gods, and without denying that others can with equal truth worship different gods. It has been called "monotheism in principle and polytheism in fact".
Monolatrism (or Monolatry): The belief in the existence of many gods, but with the consistent worship of only one deity. Unlike Henotheism, Monolatrism asserts that there is only one god who is worthy of worship, though other gods are known to exist.
Kathenotheism: The belief that there is more than one deity, but only one deity at a time should be worshipped, each being supreme in turn.
Animism:
The belief that souls inhabit all or most objects (whether they be animals, vegetables or minerals). Animistic religions generally do not accept a sharp distinction between spirit and matter, and assume that this unification of matter and spirit plays a role in daily life. Early Shintoism was animistic in nature, as are many indigenous African religions. Shamanism (communication with the spirit world) and Ancestor Worship (worship of deceased family members, who are believed to have a continued existence and influence) are similar categories.
Atheism (or Nontheism):
The belief that gods do not exist, or a complete rejection of Theism in any form. Some atheists argue a lack of empirical evidence for the existence of deities, while others argue for Atheism on philosophical, social or historical grounds. Many atheists tend toward secular philosophies such as Humanism and Naturalism. Atheism may be implicit (someone who has never thought about belief in gods) or explicit (someone who has made an assertion, either weak or strong, regarding their lack of belief in gods). Confucianism, Taoism, Jainism and some varieties of Buddhism, either do not include belief in a personal god as a tenet of the religion, or actively teach nontheism.
Agnosticism:
The belief that the nature and existence of gods is unknown and cannot ever be known or proven. Technically, this position is strong agnosticism: in popular usage, an agnostic may just be someone who takes no position, pro or con, on the existence of gods, or who has not yet been able to decide, or who suspends judgment due to lack of evidence one way or the other (weak agnosticism). The earliest professed agnostic was Protagoras, although the term itself, which literally means "without knowledge", was not coined until the 1880s by T. H. Huxley (1825 - 1895).
Humanism:
Humanism is more an ethical process, not a dogma about the existence or otherwise of gods. But in general terms, it rejects the validity of transcendental justifications, such as a dependence on belief without reason, the supernatural, or texts of allegedly divine origin. It is therefore generally compatible with Atheism and Agnosticism, but does not require these, and can be compatible with some religions. To some extent, it supplements or supplants the role of religions, and can be considered in some ways as "equivalent" to a religion.