Primary sources are the original items which have been produced by an author, artist, diarist, musician, scientist, etc. The documents or objects of primary data are studied, assessed, evaluated and commented upon by researcher or student. What is considered a primary source may vary from discipline to discipline. It may vary within a discipline because one person may use an item as a primary source and another may regard it as secondary. Every step away from the original increases the possibility of misinterpretation of the original meaning.
Primary data is that which has no precedent.
In any historical research it is the experience of those who were there. Primary literature is found in books, magazine and journal articles, manuscripts, archives, newspapers, government publications and documents, diaries, maps, tapes and other artifacts. Microform copies are sometimes used as primary sources. Book reviews, literary and scientific criticism, essays, biographical sources and bibliographies are secondary sources. Sometimes secondary sources are the only and best information available.