The Cornish language is a way that people in a place called Cornwall used to talk. It's like a secret code that only the people from Cornwall could understand.
Just like how you might have different words for things like "dog" or "cat" in different languages, the Cornish language has its own words for things. For example, in Cornish "goodbye" is "dew genough" and "thank you" is "meur ras".
But, not many people speak Cornish anymore. That's because a long time ago, everyone started speaking English instead. But some people really liked the Cornish language and wanted to keep it alive. So, they started to teach it to their kids and to other people who wanted to learn it.
Now, some people in Cornwall still speak Cornish and it's also taught in schools so that more people can learn it. It's really cool to hear people speaking Cornish and it shows how different places can have their own special ways of talking.