Theology is literally the study of God (Greek θεος, theos, "God", + λογος, logos, "study"). By extension, it also refers to the study of other religious topics. The term theology originated in Christianity, but it can also be used to refer to the study of the beliefs of other religions. This is sometimes seen as a form of philosophy.
Theology assumes the truth of at least some religious beliefs and therefore can be distinguished from the philosophy of religion, which does not presume the truth of any religious beliefs. The philosophy of religion, when it seeks to study these topics, uses reason and experience as its sources; while theology can also use religious sources such as scriptures (e.g. the Bible), traditions, etc. This is not, however, to say that one must have religious belief in order to be a theologian - though agnostic or atheist theologians are very rare. In Eastern Christianity, there is more emphasis on prayer than on intellectual thought and study as a means to learn about God. Studying God without any kind of relationship or desire for relationship with God is considered by some almost meaningless, but others would argue that one can engage with issues in terms of notions around "God" as an exercise in history, anthropology, and/or sociology, yet not have any desire for engagement in terms of the personal God offered in terms of certain forms of religion. Many of the early church fathers described the theologian as a person who "truly prays."
In response to the horrors of the Holocaust, many theologians (especially Jewish theologians) were prompted to take a harder look in terms of issues around theodicy; the theological works that were created as a response to the Holocaust have been termed Holocaust theology.
Theology is divided into several subdisciplines: