Kassites were a group of people who lived a long time ago in a place called Mesopotamia, which is now mostly present-day Iraq. They were known for their skill in making pottery and weaving textiles. The Kassites had a different language and culture than the people around them, and they ruled over some parts of Mesopotamia for several hundred years.
The Kassites were very peaceful people who liked to make treaties with their neighbors rather than fight with them. They were also very good at making friends with other cultures and learning from them. They did not leave much behind in the way of written records, so we don't know as much about them as we would like.
Eventually, the Kassites were conquered by a group of people called the Elamites, who ruled over Mesopotamia for a while before being replaced by other groups. Even though the Kassites are long gone, their influence can still be seen in the art and culture of the region today.