Siddhartha Gautama was a prince from what is now known as Nepal who lived about 500 years before Christ. His teachings formed the core beliefs of Buddhism. Those beliefs are summarized in the noble Eightfold Path:
You can learn more about Buddhism by reading a wide variety of spiritual and religious writings based on these beliefs. However, you can also read the novel Siddhartha by the great German writer Hermann Hesse. It is a short and very well written telling of the life of Buddha. I would also suggest that you watch the movie Little Buddha. Although it is not a great film, it does give you some very good insights into the life of Buddha that make it well worth watching. It was made in 1993 and stars Keanu Reeves as Siddhartha. One reason the film is worth watching is it has a great look thanks to cinematographer Vittorio Storaro and is filmed in Nepal and Bhutan. It was directed by Bernardo Bertolucci.