"Instead of nesting definitions" in docs

On this page: https://react.dev/learn/your-first-component

When a child component needs some data from a parent, pass it by props instead of nesting definitions.

all of a sudden, it says, "instead of nesting definitions". Can you explain in the docs more what is "nesting definitions" and how does it work to "attempt to pass some data and doesn't work or shouldn't be done"? I have never heard of "nesting definitions" after working with React for a few years.

https://react.dev/learn/your-first-component の “Your First Component” ページから始めて、“instead of nesting definitions.” を含む文を見つけてください。文脈を確認するため、リンク先の “Passing Props to a Component” ページを確認し、定義をネストするとはどういう意味か、なぜ props が推奨されるのかを明確にしてください。React ユーザーがこの表現と、意図されたデータ受け渡しの指針を理解できれば完了です。