If you simply input a single word the process is simple. The search engine will look for all references to that word. This will result in very large results that may be quite unusable. Normally you'll need to narrow things down with multiple words. Depending on how the search engine responds will change the result dramatically.
All search engines have documentation explaining how there particular search engine works.
These explanations are not always easily understandable. If your first attempt fails, adjust the information you provide for the query. If you still get unsatisfactory results try another search engine. Over time you will probably come to favour one or two search engines but don't forget that there are others. Be on the lookout for new engines that may better suit your needs.