Primary sources of information are original artifacts, documents, recordings, or other sources of information about a topic. They offer first hand, original evidence.
Secondary sources of information are created after an event has occurred or by someone who did not experience or participate in the event first-hand. Secondary sources often include opinions about the event or person so they have value in analyzing its importance or significance.
Tertiary sources are sources that index, abstract, organize, compile, or digest other sources. Some reference materials and textbooks are considered tertiary sources when their chief purpose is to list, summarize or simply repackage ideas or other information. Tertiary sources are usually not credited to a particular author.