When conducting research, you need to be able to distinguish between primary and secondary sources. Archival collections are different from library collections which usually contain published materials, most of which are considered secondary sources, not primary sources.
A primary source is a firsthand account created at the time of an event.
Examples of primary sources include letters and diaries; government, church, and business records; oral histories; photographs, motion pictures, and videos; maps and land records; and blueprints. Newspaper articles contemporaneous with the events described are traditionally considered primary sources, although the reporter may have compiled the story from witnesses, rather than being an eyewitness. Artifacts and specimens may also be primary evidence if they are the object of study.
By analyzing primary source materials, we can get a better understanding of past events.
Secondary sources are second hand accounts, created at some point after the event or subject being documented. Secondary sources use the information found in primary sources and create an interpretation or commentary. These are usually published works, like books or articles.