Caesar Augustus was Julius Caesar's great-nephew, adopted by Julius Caesar in his will, and named as Caesar's successor.
He was born Gaius Octavius, named after his father. He changed his name when he was adopted by Julius Caesar, as was usual at that time, to Gaius Julius Caesar Octavianus. When he became the first emperor of the Roman Empire in 27BC, he added the name 'Augustus' as well, as though four names already weren't enough!
The Roman Empire grew significantly during the 40 years that Caesar Augustus ruled, though it was also a relatively peaceful time. Remarkably, it seems that he may have died of natural causes at the age of 75 in AD14, though there is still the possibility that he was poisoned by his wife!
Caesar Augustus is a name familiar to most people from a biblical quote that we hear every Christmas: "And it came to pass in those days, that there went out a decree from Caesar Augustus, that all the world should be taxed." This was the event that caused Joseph to travel with Mary to Bethlehem although she was 'great with child'.