The Austrian Empire was a really big group of people who lived under one king or emperor a long time ago. They lived in what is now Austria but also some other countries like Hungary and Croatia.
The king in charge of the Austrian Empire was called the Emperor and he had lots of power over the people who lived in the empire. He had lots of important people who helped him make decisions like what to do when there were problems or who the empire should make friends with.
The people who lived in the Austrian Empire spoke lots of different languages and had different traditions, but they all had to follow the rules and laws set by the Emperor. They would also have to go and fight in wars if the Emperor said they had to.
The Austrian Empire was around for a really long time and it's important because it helped shape the history of Europe. But eventually, it got too big and too hard to control, so it became smaller and became the country we now know as Austria.