A model organism is a non-human species that is extensively studied to understand biological processes, genetics, and disease mechanisms. These organisms are chosen for their ease of maintenance, rapid reproduction, and genetic similarities to humans. Common examples include fruit flies, mice, and zebrafish. Researchers use model organisms to conduct experiments that can provide insights into human biology and health. By studying these organisms, scientists can identify genes, test drug effects, and explore developmental processes, ultimately contributing to advancements in fields like medicine and genetics.