Christopher Ehret is a person who studies languages and how they change over time. He's like a detective who tries to figure out the story behind the words that people spoke a long time ago.
When people speak, they create words and phrases to communicate with each other. Over time, those words can change and evolve in different ways. Christopher Ehret is interested in how and why that happens.
He uses tools like maps and databases to track the movements of people and how they spread their languages around different parts of the world. He also studies things like ancient writings and artifacts to figure out what people used to say and how they used to say it.
The things that Christopher Ehret discovers can help us better understand how our own language developed over time. It's like he's trying to piece together a puzzle that helps us see the big picture of how different languages and cultures are related.