In History, primary sources are objects and documents created or written during the time being investigated, for example during an event or very soon after. Examples of primary sources include official documents, such as laws and treaties; personal documents, such as diaries and letters; photographs; film and documentaries. These original, firsthand accounts are analysed by the historian to answer questions about the past.

Secondary sources are accounts about the past that were created after the time being investigated and which often use or refer to primary sources and present a particular interpretation. Examples of secondary sources include writings of historians, encyclopaedia, documentaries, history textbooks, and websites.