Simply put, primary sources are original materials. They are the records of events reported by first hand witnesses to events as they happened, typically by a person involved directly with the event. Diaries, interviews, letters, meeting minutes, photographs, works of art and more can be considered primary resources. Primary resources allow for insight into events that may have happened anywhere from 1000 years ago to just the other day and help to give added dimension to events for later interpretation. The difference between a primary and secondary source can sometimes be confusing; an object that is a primary source for one topic might be a secondary source for another.
Primary VS Secondary
Diary of Anne Frank - A primary source account of the experiences of a Jewish family in hiding during WWII
Textbook on WWII - A secondary source that might list the Diary of Anne Frank as a reference