After Caesar's death, a new civil war broke out. Several leaders fought each other to control Rome.
One of them was Caesar's adopted son Octavian.
Octavian Caesar defeated his rivals in 31 BC and led Rome into a new era.
Octavian brought peace to the Roman Empire and became a popular leader.
In 27 BC the senate voted to give him the title "Augustus", meaning "respected one". He also chose the name "Caesar" in honour of his adopted father. So he became Caesar Augustus. He did not call himself an emperor, but he sure was one. He had all the power.
All Augustus' successors used "Caesar" as a title. After a while the name Caesar became the word "keizer".
With Augustus, Rome was a monarchy again.