N.K. Chauhan 
All the material which has a direct bearing or can be any assistance in constructing the history of a particular period is called as historical facts or sources.
The historical sources can be of two types, i.e. Primary and Secondary Sources.
1) Primary Sources
A primary source is the evidence of an eye witness or mechanical device which was present at the time of the occurrence of an event.It is the work of the historian to convert the scattered difficult primary evidences into coherent, intelligible secondary sources.
The primary sources can be classified into the following categories:
1.1) Contemporary Records
These types of primary sources are in the form of the instruction documents, stenographic and phonographic records, the business and legal paper and autobiographies, etc.The instruction documents may be in the form of an appointment notification, and direction from foreign office to the ambassador etc.
Generally such documents have very little chance of error but it is essential to ascertain their authenticity.
The business and legal letters consists of the bills, journals, leases, tax records which gives an insight into the working of the firms as well as the persons.
1.2) Confidential Reports
The confidential reports are not intended for general audience and are less reliable than the contemporary sources.These types of reports are generally in the forms of military and diplomatic dispatches, Journals, diaries or memoirs and personal letters.
1.3) Public Reports
The public reports are meant for general public and less reliable.There are three types of public reports and each possesses a different degree of reliability, such as -
I) Newspaper reports and dispatches are more reliable which depends upon the agency from which it originated and the news paper in which it is published.
II) Memoirs and autobiographies are another public reports which are written for the public at the close of the life when the memoirs of author is fading and are therefore, not very reliable.
III) Official histories of the activities of government or business house are also an important kind of public reports. They possess incriminating material and less reliable.
1.4) Government Documents
Numerous government documents are compiled which are also a source of vital importance to the historians such as statistics about fiscal, census and vital matters which can be made use of by the historians.All these reports have first hand importance, but require proper evaluation before the use.
1.5) Public Opinion
The public opinion as expressed in editorials, speeches, pamphlets, letter to editor are another important source available to the historian.But authenticity of this must be corroborated by other evidence because public opinion may not be always reliable.
1.6) Folklores and Proverbs
The folklores (लोककथा) which reveal the stories of legendary heroes are also an important source of history.They tell us about the aspirations, superstitions and customs of the people among whom the stories developed, e.g. "Alla-Uddal" the hero Rajputana.
To make the use of these folklores the historian should not only possess a thorough knowledge of the history of the period but also able to distinguish between the legendary and authentic elements.
Similarly proverbs (लोकोक्ति) can give us an idea but scholar must have the thorough knowledge of the customs and traditions.
2) Secondary Sources
A secondary source is one in which the eyewitness or the participant i.e. the person describing the event was not actually present but who obtained his/her descriptions or narrations from another person or source.The secondary source is also of great historical importance to the historians although secondary source is itself dependent on primary sources.
They include data which are not original.
Examples of secondary sources include textbooks, biographies, encyclopaedias, reference books, replicas of art objects and paintings and so on.
It is possible that secondary sources contain errors due to passing of information from one source to another.
These errors could get multiplied when the information passes through many sources thereby resulting in an error of great magnitude in the final data.
Thus, wherever possible, the researcher should try to use primary sources of data.
However, that does not reduce the value of secondary sources.
