The indexes used by the "browse" searches in the Advanced screen of the online catalogue are alphabetically arranged lists of headings of various types - headings for authors, titles (of books, of series and of serials) and subjects. They are "Heading: starts with" type searches.
Author headings start with the author's surname. If you enter "hedley sparks" in Author browse mode, you will be taken to be referring to an author whose surname is Hedley. The correct way to enter that search is: "sparks, hedley". [Also - you are not required to use capital letters correctly.]
Keyword searches (which are available in the Advanced, Power and Basic search screens of the online catalogue) find records in which the word or words that are used in the search occur. They may occur anywhere in the record for a General keyword search to retrieve that record. They may occur anywhere in the nominated field for a keyword search limited by field to retrieve the record. A keyword search may focus on one or more of the following fields: Title, Author, Subject, Name, Series and Contents.
A phrase can be used in a keyword search, but put it in inverted commas. "HOLY COMMUNION" is a more exact search than HOLY COMMUNION.