By now you should be prepared to answer the following questions. But of course, you should be prepared to learn and improve as well.
First of all, what is a function? You may know this, but you should also know how to use a function.
There are different ways of performing different operations on functions. That is why the question “what is a function?”
And as far as functional programming languages are concerned, you should know what a function does. But if you want to use function-styleprogramming, then it is much better to come up with your own.