'The Buddha' was a real, historical person. Born as Siddhartha Gautama, he lived some ~2500 years ago in ancient India/Nepal.
The ultimate significance of the Buddha is his status as the first known person to attain [WIP] Enlightenment (it's a thing) and then go on to teach others how to do the same through his establishing, teaching, and guiding of Buddhism during his lifetime.
His teachings were extensively preserved in The Pali Canon, and Buddhism has since propagated and branched in many forms and traditions, via many countries and cultures.
The Buddha was born approximately 2500 years ago in the ancient city of Kapilavastu, in what's now North-Eastern India and Nepal.
Having lived a young life of wealth, privilege, and comparative seclusion, Siddhartha ultimately renounced his family life and status to become a wandering ascetic in search of the end of suffering through the holy traditions of the time.
In the ensuing years, Siddhartha become an ascetic of some renown, having demonstrated extreme discipline and dedication in taking the major ascetic practices of the time to their extremes (self-mortification, self-indulgence). Ultimately, though, he found these practices to be dead-ends, and abandoned them too - losing some small status in doing so.
Alone again, Siddhartha famously sat and resolved to not move until he finally achieved enlightenment. Intensely applying and exploring what he had learned and mastered in his contemplative practices up until that time, he found "the middle path" (between the extremes of self-mortification and self-indulgence) attained [WIP] Enlightenment (it's a thing), and became The Buddha ("Awakened One").
From there, he allegedly briefly considered keeping his discovery to himself, thinking that the world would not understand or accept him or his prospective teachings, but instead he resolved to teach, and thus Buddhism was born.
Even the above is a very truncated view of The Buddha's early life. The story beyond the above is more the history of early Buddhism, and both the expanded biography of the Buddha as well as early Buddhism (and the subsequent history of Buddhism) are incredibly intricate and interesting.
If you're interested in learning more, I would encourage you to seek! There are myriad resources, histories, and tellings of these stories as you would expect.
Unlike other religious figureheads, the Buddha is not revered as a God or deity, or purported to have possessed any superhuman or magical abilities. The Buddha is instead celebrated as a beloved role model and the generous root source of Buddhism, as well as a physical and aspirational representation of awakening.
The Buddha himself proclaimed to be on equal footing with those of his followers who also attained the same level of awakening, and later in his life refused to appoint anything like an heir or successor to his considerably large and influential community and followership.
"Author" of the The Pali Canon