It's very likely that for some of your college assignments you'll be required to find and use sources (like books and journal articles) that have certain qualities, such as:
Scholarly/academic (such as books or journal articles)
Popular (such as news, magazines, websites, etc.)
Primary and secondary
Any of these source types could be credible sources, but you'll need to evaluate them to determine their credibility. Typically scholarly, and especially peer-reviewed, are considered credible just by the nature of their publication process.
Extremely important disclaimer: NAU instructors don't consistently define source qualities the same way. In fact, many instructors use these words interchangeably:
So, if you are working on an assignment and you need to find sources that have certain qualities, you'll need to make sure you know how your instructor defines those qualities.