Sometimes your professor will ask that at least some of your sources be from "scholarly journals." Scholarly journal articles are typically written by experts in the field who are often associated with universities. Journal articles will often focus on an aspect of a topic, and go into quite a bit of depth. They must be peer reviewed by other experts in the field, before being approved for publication.
The databases linked here are great places to look for these scholarly articles. Remember to place a checkmark next to where it says "peer reviewed" or "scholarly journals."
Please note: for the JStor database, use the "advanced search" option, as it will limit you to content for which HACC has full-text access.