The Temple is a religious building. Every religion has its own Temple (dubbed Buddhist Temple, Christian Temple, and so forth), but they are all alike in regard to their properties. It is possible to build up to seven different Temples in a city if all the religions are present there.
In Civilization IV, a temple is defined as a building where the faithful come to worship. Christians call their temples "churches," while Muslims call theirs "mosques," and Jews call theirs, simply, "temples." Temples are far more common than cathedrals, but much less large and ornate. Even the smallest village can possess a temple.
Buddhist temples are places of worship, meditation and study; they can be found across the world. The oldest surviving Buddhist temples are in India, where the religion was first founded.
Facing Roman persecution, the earliest Christians worshiped in secret in private homes, catacombs, and the like. The Emperor Constantine I legalized Christianity in 325 AD. Though not a Christian himself as is often mistakenly claimed, Constantine I built many Christian churches across Roman territory, including the Church of the Nativity in Bethlehem, which many Christians believe is on the site where Jesus was born.
Though Confucius himself was a philosopher rather than a religious leader, over time he was accorded the status of a god and worshipped across Asia. Many temples to Confucius were constructed, some small and private, others more extensive where hundreds of worshippers could attend services. Many Confucian temples were constructed in the pagoda style of architecture.
The word "mandir" is used to denote all Hindu places of worship. In Civilization IV, that term is reserved for the larger and more ornate buildings; smaller mandirs are called "temples." Typically, a Hindu temple is dedicated to a primary Hindu deity and that deity's subordinates. Worshipers must maintain a certain level of ritual purity to enter a temple: they must not wear footwear; they must not smoke, eat or drink inside; their breath should not smell of garlic or onions; and they may enter only with the priest's permission.
In common usage, the term "mosque" is used to describe any Islamic house of worship. In this game that term is reserved for the more important and impressive structures; common mosques are called "Islamic temples." There are Islamic temples across the world. Many contain towers from which the worshipers are called to perform "salah," the five daily prayers each Muslim must perform.
Traditionally, the term "synagogue" is used to describe all Jewish houses of worship. For purposes of game clarity, Civilization IV uses the term to describe only the larger and more imposing structures; smaller religious structures are called "Jewish temples."
Temples are places of prayer and study. Worshipers attend services on the "Shabbat" (or Sabbath), the day of rest which begins at sundown on Friday and ends at nightfall on Saturday. Jewish temples are often the center of Jewish life in a community, and may serve as schools, meeting places, libraries, and so forth.
Taoist temples are often attractive, brightly-colored buildings, filled with statues of divine beings. Priests may or may not be in attendance. Taoism is a ritualistic religion, and the temple is often used for ceremonies ranging from parades to exorcisms. The ceremonies themselves tend to be loud and colorful, full of chanting, singing, clashing symbols, and firecrackers.