The term 'geological eras' refers to the divisions of time in Earth's history, which are known as EONS. EONS are the longest units of geological time and are divided into smaller units such as eras, periods, and epochs. The EONS are divided into the Hadean, Archean, Proterozoic, and Phanerozoic. Each of these EONS is further divided into eras, which are the second-longest units of geological time. Examples of eras include the Paleozoic, Mesozoic, and Cenozoic.