Along with a basic search, you can also mix Keyword(s) and search by Author, Title and Subject searches via the Advanced Search screen.
Of course, you can enter this information in a basic search, however, the basic search will still look for these anywhere in your results, searching for "Shakespeare" will get you results authored by William Shakespeare, but the results will also retrieve items like The Shakespeare Code, which means your results will be less precise, rather than more.
Using Advanced Search you can define where your search terms are to be found in the results. This means you can make a distinction between works in the style of Debussy, and those Authored by him.
Say we are looking for the Sandman graphic novels written by Neil Gaiman, if we start with a Basic search for the Keywords: Fantasy AND Gaiman AND Sandman, we will get the titles, but we will also get lots of articles on Neil Gaiman and Fantasy fiction, articles that only mention his Sandman graphic novels.
However, using Advanced search we can then change the Fields each line searches. If we tweak the drop-down fields so we were searching Keyword: Fantasy AND Author: Gaiman AND Keyword: Sandman, we will get fantasy books written by Neil Gaiman, where the book blurb mentions “From the author of the Sandman comics.”
Finally, if we search: Keyword: Fantasy AND Author: Gaiman AND Title: Sandman we will get you the Sandman comics written by Neil Gaiman (and nothing else).
As you can see, Advanced searching by using Fields can help you target your search very precisely.
Subject Headings are far more precise search terms than the default Keyword searches, and a Subject Heading directly reflects what an item is about, rather than returning incidental results. Unlike a Keyword which may be anywhere in the results, a Subject heading is only applied by someone who has read the item, and who has indexed it as being directly about the Subject.
If you are looking for material on "postmodernism," a Keyword search may return results disclaiming the article is "not postmodern," whereas a Subject heading search will only return articles about the theory of postmodernism itself (this means someone has actually read the article, and decided it is mainly about that particular Subject).
These precise terms can be difficult to discover or predict because different databases will use different terms. One way to discover Subject headings is to perform an initial Keyword search (for example: Batman), then select the Title of an appropriate source, and clicking through the "View Description" link to see the Subject headings related to that item. Either click these to search the Subject heading directly, or copy and paste the term for Advanced search.
Note: Searching "Post-modernism" in OCLC Search FAST will redirect to the accepted Subject heading "Postmodernism," and also related terms. Copy and paste these terms into the Subject heading Field in the Advanced search screen.