Primary source documents are original materials created during a specific time period or event. They provide firsthand accounts and direct evidence, such as letters, diaries, photographs, official records, and artifacts. These documents are valuable for researchers and historians because they offer insights into the thoughts, experiences, and context of the people involved. Examples of primary source documents include the Declaration of Independence, World War II letters, and ancient manuscripts. By analyzing these sources, individuals can gain a deeper understanding of historical events and the perspectives of those who lived through them.