You may be referring to an affidavit, which is a sworn declaration (often written) from a witness or other person called to testify in a legal proceding.
primary source
Primary Source
One who can give a firsthand account of something seen, heard, or experienced:a witness to the accident.The witness went at the court to provide informations about the accident.
primary source
source documents
Four examples of published document primary sources include letters, diaries, newspapers, and government documents. These sources provide firsthand accounts or official records of events, and are commonly used by historians and researchers to study specific time periods or topics.
first hand
Secondary Source.
There were thousands of first hand accounts of D-Day, many used in books . Look at WW2 in your library, you will find lots about D-Day.
The description shouldn't be there. The answer to the question is "They provide firsthand accounts of historical events."
A personal diary is considered a primary source because it provides firsthand accounts of personal experiences and perspectives. Textbooks and biographies are considered secondary sources as they interpret and analyze information from primary sources.
It's a secondary source.