In business, you often use forecasting to project sales, to estimate what future revenues will be on the basis of past history. This puts you in a position to estimate other quantities, such as cost allocations and staffing, that you need to support the revenue stream.
The term forecasting, as used here, is the result of looking back at historic data and figuring out how what came before determined what came after. That process leads to mathematical models that can incorporate your current conditions and forecast what's likely to happen next.