Facebook Prophet is an open-source forecasting tool developed by Facebook for time-series prediction. It is particularly effective for forecasting data with daily, weekly, or yearly seasonal trends. Prophet uses a decomposable model with components for trend, seasonality, and holidays, allowing it to handle missing data and outliers efficiently. It is designed to be highly flexible, enabling users to easily incorporate external regressors. Prophet is widely used in business forecasting for applications like sales prediction, traffic forecasting, and resource planning due to its simplicity and accuracy in handling large datasets.