A citation describes a source and provides information about it in a standard format. Citations are located in the bibliography, works cited, or references of an article, book, chapter, encyclopedia article, etc. Citations enable the reader to identify and find any sources listed.
Citations also give credit to other authors for their ideas, rather than making it look like the author of the work was the original source for an idea.
Generally, citations tell you the title of the work, who wrote it, the date it was published, where it was published, and who published it.