Primary sources are first-hand accounts, original manuscripts, records, or documents produced from the time period at hand. Some examples of types of primary sources include the following:
Personal papers, memoirs, diaries
Newspaper articles from the time period
Original records on science experiments
These may be available in their original form or they may be reproduced or reprinted in another book.
Learn more about primary (and secondary!) sources through the links below from TeachingHistory.org:
Listed below are various K-12 level online databases that include a variety of primary sources.