There's a difference between THE Buddha and A Buddha. THE Buddha was the original teacher of the doctrine - a guide to behavior and existence in accordance to the universe (Dharma) - that is known as Buddhism. Buddha, or Gautama Buddha, also known as Siddhārtha Gautama, Shakyamuni Buddha, or simply the Buddha, born in 567 BC, was an ascetic and sage, on whose teachings Buddhism was founded.
Anyone can become a Buddha. The first step is to change one's way of life trying in as much as possible to follow the Dharma - behaving in a manner corresponding to a virtuous individual. An individual who has decided to seek Buddhahood (reaching the state of Buddha) is called a bodhisattva. A bodhisattva will live, die and reincarnate for as long as it takes for him/her to become one with the universe - in other words achieving detachment from the illusion of the "real world" regular people live in and by.
Buddhism is a guide to living in a way that brings the universe into harmony. It's not a religion. Even though Buddha(s) are represented as sitting in heaven-like palaces among the clouds, it does not mean they are gods as the term is understood in other religions. Followers pray in Buddhist temples seeking help from those enlightened before them, so that they may receive guidance in their way to a more virtuous life. Praying to the Buddhas is not meant to ask for fortune, the solution of our problems or the cleansing of our sins.