Augustus was born was born on September 23 in 63 BC and he lived a long and eventful life. He died on August 19 in 14 AD. There is so much that Augustus accomplished in his life that I will only mention the most significant.
First, most historians of Rome consider Augustus to be the first emperor of Rome. So, we can say that under Augustus the Republic came to an end. Moreover, he established the empire during his long life. For this reason alone, he was a pivotal figure in Rome.
Second, Augustus brought peace to Rome after over one hundred years of conflict among the aristocracy, starting with the death of Tiberius and Gauss Gracchus. The time period that he ushered in was also called the Augustan peace.
Third, part of the reason why he is so famous is because he was a great patron of the arts. So, people like Virgil and Horace wrote poems about him as a savior figure.
If you want to read more about Augustus and his accomplishment, you can look at how he wanted to be remembered in his work, the Res Gestae.