You can use the reference list of an article or book to find related literature (snowball method).
When you have a list of publications, for example after performing a topic search in Scopus or Web of Science, this citation information helps you to identify key publications (as measured by the number of citations received) and other potentially relevant publications:
Click on the picture to enlarge it.
Example of a Citation Map, created in Web of Science. On the left hand you find the reference list of the article in the middle (Zwaan, R. A. (2014). Embodiment and language comprehension: Reframing the discussion. Trends in Cognitive Sciences,18(5), 229-234. https://doi.org/10.1016/j.tics.2014.02.008) and on the right hand the articles citing Zwaan's article (at the time this picture was made, the article has more citations now). [Unfortunately, the Citation Map feature has been retired by Web of Science, it is no longer possible to create a citation map.]