Primary sources are documents or objects that are original and provide direct, first-hand evidence.
In scholarship, a document or record containing firsthand information or original data on a topic, used in preparing a derivative work. Primary sources include original manuscripts, periodical articles reporting original research or thought, diaries, memoirs, letters, journals, photographs, drawings, posters, film footage, sheet music, songs, interviews, government documents, public records, eyewitness accounts, newspaper clippings, etc. (The Online Dictionary for Library and Information Science)
Sample search terms could include:
Secondary sources analyze, discuss, and comment upon primary sources. Disciplines define primary sources differently. To the scientist, they might be reports of original research or personal papers; to the journalist, they might be interviews or letters. The researcher’s relation to source is important in terms of proximity and determination of source type. Format, content, use, and interpretation must be considered.
Any published or unpublished work that is one step removed from the original source, usually describing, summarizing, analyzing, evaluating, derived from, or based on primary source materials, for example, a review, critical analysis, second-person account, or biographical or historical study. Also refers to material other than primary sources used in the preparation of a written work. (The Online Dictionary for Library and Information Science )
If you are unsure if something is a primary or secondary source, ask your instructor!