What does the "cdw" do exactly in the canned Search for "Recents"?
The cdw at the end of the query string means the comparison should ignore case, diacritics, and width (which is mostly relevant for text with Asian characters).

1st source: How can I find files by content in mac os x?  


  Use this modifier... To specify a comparison that is...
  c                             Case insensitive.
  d                             Insensitive to diacritical marks.
  w                            Word-based. In addition, the comparison detects transitions from lower-case
                                 to upper-case.
  t                              Performed on the tokenized value. For example, values passed directly from
                                 a search field are tokenized.


2nd source: CSSearchQuery