When performing research, most writers will come across a variety of information from a variety of different places. All of these sources can be classified as either primary or secondary sources.
Primary Source: A primary source is an original study, document, object, or eyewitness account. In other words, this is the source where any given information first appeared. For instance, if a scientific study is performed, the primary source is the initial report that is prepared by the scientist(s) who performed the research.
Secondary Source: A secondary source is a document that is written about the primary source. These are
often documents that report, analyze, discuss, or interpret primary sources.
Depending on the essay being written, both primary sources and secondary sources may be acceptable types of sources. For instance, if a writer is writing an argument essay about the need to pass a certain amendment, she can quote or paraphrase both the amendment itself (the primary source) and the opinions or studies of others that analyze the effectiveness of the amendment (secondary source).
Finding Primary Sources:
Even though secondary sources are often acceptable, primary sources are often better than secondary sources, and there are times when primary sources must be used. While most of the sources that are found during research are secondary sources, it is often possible to also track down the primary source. To do this, look at the references, works cited, bibliography, or internet links (for an internet source) provided in a secondary source. These will often lead you to the primary source itself; after all, these writers have to document their sources just as you have to.