Q: Was the institution of monasticism initiated by Shakyamuni？
A: No. By the time of the Buddha, renunciation of household life for religious self-cultivation was already commonplace within academic and philosophical circles. But because of the Buddha's status as a prince, his renunciation gave a boost to the practice. Buddhist who have left home life are generally called monks or nuns.

Q: Are such monastics the equivalent of the clergy of other religions?
A: Buddhist monks and nuns are merely those who renounce the household to practice for the sake of liberation (from samsara). They are not intermediaries between deities and human beings.

Q: What kind of life should a Buddhist monastic lead?
A: A monastic should lead a pure and frugal life. He or she should strictly uphold the precepts of abstaining from killing, stealing, sex, lying, hurtful speech, frivolous talk, alcohol, untimely eating and the use of perfumes and adornments. Other observances include refraining from singing and dancing or watching others sing and dance; sitting on high chairs and sleeping on luxurious beds; accepting precious things like gold, silver, elephants and horses.

Monastics should not have private possessions except robes, an alms bowl, razor, water-filter, needle and thread and other such necessities. Nor should they do business, engage in fortune-telling or spuriously display magical wonders. During the six periods of the day (morning, noon, dusk, nightfall, midnight and dawn), they should devote themselves to diligent study and practice of the Dharma, after allowing time for sleeping, alms rounds, food and drink, and labor.

From Buddhism for Beginners – Questions and Answers