In basic search, Bag of Words mode employs special relevancy ranking features which emphasize phrase and proximity matches with the search phrase, even though the user did not employ quotes or proximity operators.
The three queries combined with the OR operator into a single query, and the relevance ranking are designed to ensure that the results from group 1 always rank above group 2, which rank above group 3.
The search results pages for banner and advanced search allow you to sort the search results by last-modified date, folder, or object type.