Google Scholar is a web search engine.
Google Scholar provides a simple way to broadly search for scholarly literature. From one place, you can search across many disciplines and sources: articles, theses, books, abstracts and court opinions, from academic publishers, professional societies, online repositories, universities and other web sites. Google Scholar helps you find relevant work across the world of scholarly research.
Where is this?
Searching by image allows you to do a reverse image search and discover all sorts of content that's related to a specific image. For example, search using a picture of your favorite band and see search results that might include similar images, webpages about the band, and even sites that include the same picture. (Google)
Question: Why would you use Google Book Search?
Answer: Google Book Search (unlike WorldCAT) searches the full-text of the books in its inventory. WorldCAT is limited to searching only title, author, subject heading and other specific and limited information about a book.
Because Google Book Search lets you search within books, you can see a table of contents or an index or just a portion of a book. You can then locate the book in a nearby library.
Wikipedia may provide accurate background information, but it must be verified and should not be cited as a source. The bibliographies and related links that follow Wikipedia entries can be very useful and reliable sources that are often appropriate to cite in research papers.
See additional pages related to Source Types, Scholarly Journals, and Primary vs. Secondary Sources.