Another way to think about sources is to consider them from the point of view of how you might use them. The writing composition scholar Joe Bizup has developed an approach that many people have found useful called BEAM. For an overview of the BEAM approach, take a look at the following website from Hunter College - https://library.hunter.cuny.edu/research-toolkit/how-do-i-use-sources/beam-method - then watch the videos below.