Short answers, pulled from the story.
Theism is broadly defined as the belief in the existence of at least one deity. The term was first formally used by Ralph Cudworth (1617-1688), who defined theists as those who affirm that a perfectly conscious understanding being, existing from eternity, was the cause of all other things.
The word theism derives from the Greek theós (or theoi), meaning "god" or "gods." Ralph Cudworth introduced the term as a philosophical label in the 17th century.
Theism includes belief in a deity who may engage in revelation and intervention, while deism holds that one God created the world but does not alter the original plan for the universe. Deism rejects supernatural events such as prophecies and miracles, grounding religious belief in human reason and observed features of the natural world instead.
The main types include classical theism, monotheism (belief in one deity), polytheism (belief in multiple deities), pantheism (the universe itself as divine), autotheism (divinity within the individual self), and deism. Subdivisions such as henotheism, monolatrism, pandeism, and dystheism map finer distinctions in how people relate to divine beings.
Soft polytheism holds that different gods, such as Odin, Zeus, and Indra, may be cultural expressions of the same underlying deity, a view called omnitheism. Hard polytheism insists that gods are distinct, separate, real divine beings and rejects the idea that all gods are one essential god.
The mathematician Joseph Raphson coined the term pantheism in 1697. The idea was later popularized in Western culture through the philosophy of Baruch Spinoza, particularly his book Ethics, and had also been expressed in the 16th century by the philosopher and cosmologist Giordano Bruno.