A primary source is a document, speech, or other type of evidence written, created or otherwise produced during the time under study. Primary sources are original documents or objects; they are the raw material or first-hand information.
As you are searching the databases, you will find primary sources in the form of original research articles. Primary research articles can be identified by a standard format that typically includes sections titled Methods (or Materials and Methods), Results (usually including charts and statistical tables), and Discussion.