Primary sources are original works. These sources represent original thinking, report on discoveries, or share new information. Usually these represent the first formal appearance of original research. Primary sources include statistical data, manuscripts, surveys, speeches, biographies/autobiographies, diaries, oral histories, interviews, works or art and literature, research reports, government documents, computer programs, original documents (birth certificates, trial transcripts...), etc.
Secondary sources are usually studies by other researchers. They describe, analyze, and/or evaluate information found in primary sources. By repackaging information, secondary sources make information more accessible. A few examples of secondary sources are books, journal and magazine articles, encyclopedias, dictionaries, handbooks, periodical indexes, etc.