A primary source is any source of information created during the time under study. These include artifacts, photos, eye-witness accounts, unedited cell phone videos, and certain types of writing like diaries and journals.

For a list of common primary sources and questions to help you determine if the source is a primary source, click here.

Secondary sources address and analyze events and topics after they have happened. Encyclopedias, magazine articles, and most books are secondary sources. They will often cite or quote primary sources.

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The answer to this is dependent upon your research question/thesis, your audience, and the method you will use to present your findings.

A report on climate change might require raw data about glacial melt and average seasonal temperatures over time as well as reports on natural disasters assumed to be related to climate change. A documentary on a person's life would make good use of transcripts of interviews with the person, photos, and journal entries if available, alongside biographies written on the subject.

Thorough research will rely on both primary and secondary sources of information.