Popular Journals (magazines) are the journals you typically find on newsstands and grocery store checkout lines. Their articles are written and edited by journalists without particular expertise in the field of study. You will usually want to avoid these unless told otherwise.
Academic/scholarly journals, on the other hand, contain articles written by scholars who are experts in that discipline. They often go through a rigorous process called peer-review where they are evaluated (sometimes multiple times) by other scholars in the same field before being published. These are the articles your professors usually want. This page should help you find where to look for them.
Google Scholar is a helpful alternative source for finding authoritative academic articles. There is no Advanced Search in Google Scholar, so if you have multiple terms, you must connect them in one line using your Boolean Operators (and, or, not). For example, "capital punishment" AND juveniles OR adolescents
Research often works best when you search in a variety of places. I recommend trying some of our GALILEO databases in addition to searching Google Scholar. Sometimes one option works better than the other. Other times, you may find some extra articles that boost the quality of your paper or assignment by checking Google Scholar as well. You can also find open access articles here that you might otherwise miss.
GALILEO is a portal where you can search for a wide range of types of sources...all from one single database. Unlike most of the databases listed in the suggested databases section above, which is more targeted to your subject, GALILEO Discover is broad and covers most every subject you can imagine. As mentioned, it's good to try different options, including this one; however, you may find your research easier and more manageable by focusing on the databases in the "suggested databases" and "additional databases" sections.