A primary source is an original, firsthand account or evidence about an event, object, person or work of art. These are factual and are usually created during or close to the event or time period. This can include eyewitness accounts, data, diary, interviews, letters, legal documents, audio and visual recordings, speeches and artwork.
A secondary source is an analysis or interpretation of a primary source. Examples include biographies, literary criticisms and book reviews.
An example in history would be a primary source: Recorded interview with Choctaw American Indian vs a secondary source: Journal article about Native Americans who served in WWII.
Primary sources enable you to get as close as possible to what actually happened during an historical event or time period.
Primary sources include memoirs, diaries, letters, interviews, and other first-person accounts. Paintings and music created during the time period you are studying are also primary sources.
Searching for primary sources:
Many of the other databases and websites available will have Primary Sources, do not limit yourself to these!