Panel data is a type of data that combines both cross-sectional and time-series information. It consists of observations on multiple subjects, such as individuals, companies, or countries, collected over several time periods. This allows researchers to analyze changes over time while also comparing different subjects. One of the main advantages of panel data is that it helps control for unobserved variables that may affect the results. By observing the same subjects repeatedly, researchers can better understand trends and causal relationships, making it a valuable tool in fields like economics, sociology, and health studies.