The impact of this is that none of the types or elements within Book are reusable. The region of the schema where the Title and Author element declarations are applicable is localized to within the Book element. Everything is bundled together into a tidy, single unit. The components which make up Book are visible to other schemas, and to other parts of the same schema. The impact of this is that the types and elements within Book are reusable.
All components have global scope.
Everything is laid out and clearly visible. I am sure that there are other characteristics that I am missing.