A cohort study is a type of observational research where a group of people, known as a cohort, is followed over time to observe outcomes related to specific exposures or risk factors. Researchers collect data on the participants' health, lifestyle, and other variables to determine how these factors may influence the development of diseases or conditions. These studies can be prospective, where participants are followed into the future, or retrospective, where researchers look back at existing data. Cohort studies are valuable for identifying associations between exposures, such as smoking or diet, and health outcomes, like heart disease or cancer.