Forecasting is a way of using historical data and future business plans to forecast the future. A forecast will reveal where the business is going to. Forecasts are revisions to the finalized budget. i.e. You have a 2015 annual budget and your 2015-Q1 Forecast would be your revisions to the Q1 budget figures for the 2015 year. However you would still have both your annual budget and your forecasts as finalized documents for reporting and comparison purposes.