Web search engines employ "spiders" or "robots" that crawl electronically to collect web sites (e.g. Google.com or Bing.com) and then add them to their catalog. Using a search engine is similar to searching the index of a book. The researcher enters a word and the engine retrieves records with keywords or phrases matching the term entered. Although valuable for locating obscure information, keyword searching can result in large unwieldy lists and may retrieve terms out-of-context.
For example, a search using the term "nursing" may retrieve sites related to nursing as a professional discipline as well as sites that use "nursing" in other contexts (lactation, commercial sites selling uniforms, home health care agencies, etc.).
Each search engine has its own rules for determining how sites are collected and arranged and how search results are ranked according to relevance. Some rank based on frequency of occurrence in retrieved documents; others rank based on how frequently a site is linked from other sites. Search engines have different rules for entering a search string, using boolean connectors, use of quotation marks for phrases, truncation symbols, etc. So this means that your search statement can affect results dramatically.
Some search engines also include a subject directory of the included sites. Look for the "help" link on the search engine home page to determine how to enter a search.
What about Google Scholar? You may know that scholar.google.com is a subset of the larger Google database. Generally, scholar.google.com is not helpful for conducting a literature search for articles because it lacks the filtering functionality discussed in Lesson 3. It is a helpful tool for locating a "known item." For example, if you know an author, part of a title, the journal name, or other citation information, try pasting those details into scholar.google.com and see what you retrieve.
Researchers should always consider using several search tools because no one search engine covers the entire contents of the web.