Google and Google Scholar are separate search engines. While we discourage you from citing webpages and other resources discovered through a Google search, those discovered through Google Scholar are much more likely to be peer-reviewed. But "much more likely" does not mean that they always are. Just remember that you will have better results if you use a subject-specific database, like the JSTOR, Business Source Elite, socINDEX, or Academic OneFile.
Google returns results on the basis of popularity. While popular beliefs are sometimes correct, we can all think of many instances when they are not correct. Since the internet itself -- the source of all of Google's results -- includes all sorts of misinformation, one cannot be certain that results returned from Google are absolutely reliable.
Google is fine for our everyday use: In everyday life, we often use Google to find generally agreed-upon facts about a topic. But generally agreed upon topics aren't the focus of academic scholarship: scholars make arguments that often challenge presupposed facts, and need extremely reliable sources to strengthen their arguments. But all too often, the sources produced by Google do not provide enough evidence to verify the reliability of the information and facts they publish.
Also, academic articles often will not appear on websites searched by Google, because they are stored in subscription-only databases that provide limited access. Google Scholar (a *different* search engine) will find some articles, but it's best to talk with your professor or librarian about what sources to use.
Ultimately for your papers and projects, it is best to use books, journal articles, reports, and other information sources (print and electronic) that are written and published by verified experts in the "peer review system."
Wikipedia makes certain efforts at reliability that search engines like Google do not, including its own system of peer-review. Still, Wikipedia has different priorities than an academic peer-reviewed resource, and therefore it shouldn't be used in place of an academic source. Wikipedia's design trades absolute reliability for convenience and quick updating. You can never be certain that what you read on Wikipedia doesn't include misinformation that has yet to be corrected. Likewise, while Wikipedia does include a system for citation and the editorial evaluation of its entries, its real-time and open updating means that you can never be absolutely certain you're reading good information.
But perhaps most important is the fact that Wikipedia is an encyclopedia. Encyclopedias are general information sources best used for gaining a quick overview of a topic and finding a list of resources and topics to guide you in further exploration. Encyclopedia articles generally avoid controversy, and the low level of detail provided by an encyclopedia is not going to be sufficient for your academic work.