A geological era is a significant time period in Earth's history, characterized by distinct geological and biological events. The geological time scale divides Earth's history into several eras, such as the Paleozoic, Mesozoic, and Cenozoic. Each era is further divided into periods, epochs, and ages, allowing scientists to study the evolution of life and changes in the planet's surface over time. Geological eras are determined by major changes in the fossil record, climate, and geological formations. For example, the Mesozoic Era is known as the age of dinosaurs, while the Cenozoic Era is marked by the rise of mammals and birds. Understanding these eras helps scientists piece together the history of Earth and its life forms.