Whenever one is writing any kind of academic or non-academic material, it is always important to acknowledge where they got their material from. If they do not acknowledge where they got the information from then they could be held on charges of plagiarism. That is why a citation is so essential. The citation can be given for both a published source as well as an unpublished source. In most cases the citation is something as simple as an abbreviated alphanumeric expression. A proper citation also helps the reader to judge if the references cited by the author and examples that he has quoted are valid or not and how well they complement his work.
In academia there are many different types of citations. Many famous institutions in the United States and in the United Kingdom have developed their own way of giving citations to their work. The most well known methods of acknowledging someone else’s work are the Oxford style, the Harvard style, American Sociological Association or ASA style and American Psychological Association or APA style. It is up to the comfort level of the writer as to which style he wishes to use. On the other hand there are also certain academic institutions that have laid down specific styles that their students and scholars need to use for their research material. The authors who are a part of those institutions need to use only that style for all their written works.
What kind of things go in to a citation? It can be the name of the book or the author who wrote that book. It could also include the date of publication and in some cases even the specific page number. If the material has been taken from a journal then it would include the journal name and the date on which it was published. If the work has been derived from a newspaper then it should include the name of the columnist who wrote it and the date on which it was published. There are also instances where the author would use a line from a poem or a scene from a play. In such cases the name of the poem, the poet or the play and the playwright should also be given. It is essential for academic editors to be well versed with all the various citation styles so that they can check if the writer has used them correctly or not.