Secondary sources differ from primary sources in that they are:

Secondary sources are defined as accounts or interpretations of events that have been created after the fact. These sources analyze, interpret, or summarize information derived from primary sources, which are direct evidence from a specific time period, such as letters, artifacts, or first-hand accounts of events.

By being written after the event has occurred, secondary sources provide context and insight that help to understand the significance of the events but are not original testimonies themselves. They help scholars and the public explore historical events through the lens of analysis and synthesis of multiple primary documents or actual occurrences.

In contrast, first-hand accounts of an event represent primary sources, making the distinction between these types of sources clear. Sources created before an event would not qualify as either primary or secondary concerning that event. Additionally, items like letters or artifacts, while valuable, specifically reflect primary sources rather than the characteristics of secondary sources.