Using quotations in a search assures that the search only returns a match if it finds certain information in a certain order, which is done to limit the possibility of numerous, irrelevant matches. A search entered as:
Jan 2005
would return matches on any date field with the month of January, any date with the year of 2005, as well as any file record containing the number 2005 or the name Jan. This will likely return many more matches than necessary.
Using quotes narrows the search. Entering the search as:
"Jan ?? 2005"
would limit results to date fields for the month of January in the year 2005. [Technically, the search would also return any instance of the specific string Jan ?? 2005 - but the presence of this exact data string is highly unlikely in any data set].