Google is a search engine for the web. You can find just about anything, including scholarly research articles. Google is especially amazing when it comes to locating documents and information produced by non profit organizations and the federal government. Google is therefore a fantastic way to find what librarians call "grey literature" - literature that is not indexed or easily findable in traditional publishing venues.
However, as much as we love Google, it is not generally considered an academic research tool. Not all information is freely available, and you will miss out on important research & data if you limit your search only to Google or any other web browser.
GoogleScholar however, is a bit different. GoogleScholar is designed to provide access to the scholarly literature. But it can be a tad tricky to figure out what's included and what is not included in your search results. Google Scholar states that it "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." But what exactly are you searching?
With other fee based information sources, like the databases from Ebsco or ProQuest, or even free sources likes PubMed, you can learn about the coverage of the database to better determine the completeness of your search. You can also generally limit your search results to peer reviewed journals up front with a licensed database, so you know your results are limited to scholarly information resources.
You can definitely use GoogleScholar as part of your research process. In fact, its really handy to double check on journal articles that the library does not have a subscription to but which the author may have made available through a creative Commons license etc. Sometimes you get lucky!
The bottom line is that both Google & GoogleScholar are great places to start your search process, but don't rely solely on Google to find all the answers. Especially if you are trying to find the scholarly research articles, its best to start with the tools provided by the library that are specifically designed to meet the needs of researchers and educators.