The geological time scale is a system used by scientists to organize Earth's history into different time intervals. It divides the planet's 4.6 billion-year history into eons, eras, periods, epochs, and ages, helping to understand the timing and relationships of geological and biological events. Each division is marked by significant changes in the Earth's geology or the fossil record, such as the extinction of the dinosaurs at the end of the Cretaceous period. This scale allows researchers to communicate about Earth's past in a structured way, making it easier to study the evolution of life and the planet's changing environment.