The Tertiary period, also known as the Cenozoic era, is a geological period that lasted from 65 million years ago to 2.6 million years ago. During this period, mammals and birds evolved, and the earth's climate underwent significant changes, including the formation of glaciers. Synonyms for the Tertiary period include the Age of Mammals, the Age of Cenozoic, and the Quaternary period. These terms emphasize the importance of the evolution of mammals during this period and the geological change that took place. The Tertiary period is a vital part of Earth's history, and understanding it can give us valuable insight into the planet's climate, ecosystems, and evolution.