Citation is an integral part of any academic piece of writing. Citation is defined as a method to acknowledge the source of the idea. University of Pittsburgh's library guide describes a citation as "a way of giving credit to individuals for their creative and intellectual works that you utilized to support your research."
Citations are authorized methods to give credit to the source of knowledge. It is the ethical and legal duty of any scholar who wants to adopt an idea from other authors to work while authenticating his own hypothesis or providing evidence for an argument. If you don't cite the source of information used, work will fall into the category of plagiarism. Plagiarism is a serious offense with frightening consequences. You are required to cite sources in the introduction chapter, review of literature, dissertation conclusion (in the case of introducing a new idea), and references.
It is imperative to understand when to cite and when not to. You don't need to cite when using general knowledge in your dissertation, for example, the radiation of sun reaches earth in 8 minutes is a piece of general information, so you don't need to cite such information. Any historical event that is confirmed by numerous sources also does not need any citation. The dissertation conclusion also does not require citation unless introducing a new idea.
There are different styles of citations implemented across various frontiers of academia. Different journals will ask you to cite differently. Universities issue guidelines for student papers guiding students to follow a specific format and citation style. Across various fields of knowledge, different styles of citation are used. There are three ways you will use while composing your research article, essay, or dissertation.
In-text or parenthetical citation: you directly include the source in the text by enclosing the last of the author, date of publication (just year usually), and page number (optional). This method is helpful while paraphrasing as the flow of writing is not disturbed while citing the source.
Note citation: In this method, you mention the source of as endnote or footnote. Footnote is marked with an asterisk at the bottom of the page. This method provides a clean look to the document, while readers are prone to missing out on the source of information.
Numeric citation: In this method, a small numeric is added as a superscript in the text (can be hyperlinked to the reference page in case of online documents), each digit depicts a different source. Sources are arranged numerically in a reference page. It is vital to use the correct number of sources while citing. This method is often used in scientific papers, and most medical journals require this citation technique.
Another noteworthy aspect is abiding by the rules generally implemented by your discipline, e.g., APA (American Psychological Association) style is used in education, psychology, and social sciences, whereas MLA (Modern Language Association) style in humanities and Chicago author-date style in sciences.