I’m new to React, and struggling to understand this error.

I’m looking through some existing code and see this interface:

interface Props {
    above?: React.ReactChild;
    //...
}

ReactChild is struck out with the message 'ReactChild' is deprecated. - This type is not relevant when using React. Inline the type instead to make the intent clear.

Looking around, it seems the fix is to replace ReactChild with ReactNode, but can someone explain the error please…

What does “Inline the type” mean?

Thanks!