Google Scholar searches the full text of millions of journal articles from thousands of journals... plus books, theses, patents, legal decisions, PDFs on university websites and other information on the web that Google categorizes as "scholarly."
It can be a great resource for finding journal articles, although it does not provide the fine-tuned searching capabilities of some of the specialized search tools.
Never pay for an article you find online!!! If you go to http://scholar.google.com from your personal computer, you will probably be asked to PAY for journal articles. Don't do it!
Access Google Scholar via the library's link, then validate yourself as a UM student. Do your search and you'll see "Availability at UMichigan" links in the results that will bring you to the articles FOR FREE!
Here's how the screen will look if you log in via the library: