Einstein Forecasting uses machine learning to analyze historical opportunity data and generate predictions for how much revenue a sales team can expect to close in a given period. The predictions are based only on the standard Close Date and Amount fields of the opportunities, so any custom fields or other factors are not taken into account. The predictions are only shown when the user is in the forecasting hierarchy, which means that they have a forecast role assigned to them and they can view forecasts for themselves or their subordinates.