Q. What does prehistory mean?

Here is a definition from the Oxford Dictionary of World History:

The history of the time before written records were kept. The only source of evidence concerning early societies is archeological. It thus covers an immense period that begins with the study of early hominids and the emergence of Homo sapiens. It is divided into the Stone Age (Paleolithic, Mesolithic, and Neolithic), the Bronze Age, and the Iron Age. History, based on written records began c.3000 bc in Egypt and Mesopotamia.