Prophet is an open source framework from Facebook used for framing and forecasting time series. It focuses on an additive model where nonlinear trends fit with daily, weekly, and yearly seasonality and additional holiday effects. Prophet is powerful at handling missing data and shifts within the trends and generally handles outliers well. It also allows you to accumulate exogenous variables to the model.
The Prophet Model
Prophet uses a decomposable time-series model.
y(t) = g(t) + s(t) + h(t