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At least in the Westernized version of Buddhism I have heard, Buddha is not a deity. He is a man who achieved enlightenment in the Hindu sense in one lifetime instead of in many reincarnations in a state of self-awareness. He achieved this by living many different lifestyles including that of a decaying waterfowl. After enlightenment, he recognized his unity with the universal oneness, or atman. He thus got to stop being reincarnated, just like many other people who had achieved enlightenment over many lifetimes. Since the original Buddha, several other Buddhists have accomplished this feat and are thus called Buddha as well (i.e. the fat LaughingBuddha of China). If anything, the name for the sole deity in the universe is "atman".
- Some versions of Buddhism emphasize the Hindu legends more than others. The version you heard seems to be closer to the Hindu ideas of Buddhism. Most other versions do not focus on atman or reincarnation. Instead, the core of Buddhism is considered to be the teachings such as the NobleEightfoldPath and the FourNobleTruths.
- Also, while it is considered possible to achieve the same enlightenment as the historical Buddha, most Buddhists would not call those enlightened ones "Buddha"--that title is generally reserved only for the historical Buddha.
Buddhism has a whole bunch of branches, and some of the less-philosophical-more-ritualistic ones have him as a deity.