For example, a search for relevant information on this blog's focus of Library 2.0 in the academic setting could begin with a search query such as this:
What are some things that academic libraries are doing to implement Library 2.0?
And the core concepts within that query could be:
Library 2.0 . . . academic libraries . . . . implementation
Seeking synonyms for those core concepts, and linking them together with Boolean connectors, could yield something like these 3 search sets:
s1 = library 2.0 OR library technology OR internet technology
s2 = academic librar* OR university librar* OR research librar*
s3 = implementation OR program implementation OR polic*
The * represents truncation or a way to expand the search by telling the database algorithm to look for all words that begin with "libr," as in "library," or "libraries," or "librarian," and so on. The asterisk (*) is what this particular database, WorldCat, uses to indicate truncation.
The graphic I've posted here shows these 3 search sets entered into the WorldCat database search fields and further connected with the Boolean AND connector. (Click on the image to see a larger, clearer view.)

I had not indicated any particular field within the database records, so this would return the largest possible number of results.
However, the search shown returned 1,864 "hits" or results. This is too many returns -- I'll go back and use some of the WorldCat limiters to narrow my search. The first hit is shown here, and it makes me wonder how it is connected to what I'm looking for.
(When I investigate the first return, I find that the keywords are found individually, NOT as phrases as I thought I was indicating [i.e. it finds the word "library" in the bibliographic description of the item, and "2.0" somewhere in the description, but NOT as "library 2.0" together]. As I narrow those results, I'll try to sharpen the focus as well.)
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -