Geological time scales are systems used by scientists to describe the timing and relationships of events in Earth's history. They divide the planet's 4.6 billion-year history into different segments, such as eons, eras, periods, and epochs, making it easier to study and understand the changes that have occurred over time. These scales are based on significant geological and biological events, such as mass extinctions and the formation of major rock layers. For example, the Paleozoic Era is known for the emergence of early life forms, while the Mesozoic Era is famous for the age of dinosaurs.