There are three main classifications of information sources: primary, secondary, and tertiary. Primary sources come directly from the time period being studied and were created by people with firsthand experience. Secondary sources provide secondhand accounts, analysis, and interpretation of events. Tertiary sources summarize and synthesize primary and secondary sources to provide background information on a topic. When evaluating information, it is important to consider the reliability, accuracy, value, author, and timeliness of the source.