A temple is a building reserved for spiritual rituals and activities such as prayer and sacrifice. Religions which erect temples include Christianity, Hinduism, Buddhism, Sikhism, Jainism, Islam, Judaism, Zoroastrianism, the Baha'i Faith, Taoism, Shintoism, Confucianism, and ancient religions such as the Ancient Egyptian religion and the Ancient Greek religion. The form and function of temples is thus very variable, though they are often considered by believers to be in some sense the "house" of one or more deities. Typically offerings of some sort are made to the deity, and other rituals enacted, and a special group of clergy maintain, and operate the temple. The degree to which the whole population of believers can access the building varies significantly; often parts or even the whole main building can only be accessed by the clergy.