Primary sources are an accounting of what an individual saw or did. A person's diary of their life is a primary source, as is a newspaper article written by a journalist who was at the event. Journal articles and conference proceedings describing original research are primary sources because they are the first-hand description of the experience.
Secondary sources write about what they learned from primary sources. When you read an article about an event and then write about it in your assignment, you are creating a secondary source. Most books and articles are secondary sources.
