Okay kiddo, so there are many different languages in the world, right? And some of them are related to each other, like cousins or brothers and sisters. The Indo-European language family is one of these big groups of languages.
Now, in these languages (like English, Spanish, Hindi, and many more), there is a special kind of word called a copula. This is a word that connects two other parts of a sentence. It's like a glue that sticks them together.
Let's take an example. If we say "John is happy," the word "is" is the copula. It connects the subject (John) with the adjective (happy).
But in some Indo-European languages, the copula behaves a little differently depending on the situation. For example, in some cases it might be a different word altogether, or it might even disappear completely.
So to sum it up, the Indo-European copula is a special word that helps put two parts of a sentence together in some languages, but it can act differently in other languages.