Documentation is an art of giving exact Bibliography entries for both primary and secondary sources used for the research paper. The research paper is generally based on primary and secondary sources.
Primary source:
The primary source includes statistical data, historical documents and works of  literature or art. For example: if a researcher is working on the novel of Jane Austen, her novels are ‘primary source’.
Secondary Source:
Secondary Source is the examination of studies that other researchers have made of a subject. It includes books and articles about political issues, historical events, scientific debates or literary works.