A Forecast is typically what you expect to sell, the MPS (Master Production Schedule) is typically what you plan to make.
The Forecasts can optionally be Consumable (Acumatica calls them Dependent). If you forecast 100 units next month, but then get a sales order for 20 for that time period, if that Forecast is Dependent, then Acumatica will only forecast 80, if the Forecast is Not Dependent, then the forecasted amount is still 100.
Master Production Schedules are Not consumable or dependent on sales orders or other demand.
It sounds like you want to use Forecasts. Forecast can be weekly, monthly or yearly or be a one time forecast amount. The same Stock Item can have multiple forecasts for the same warehouse or different forecasts for each warehouse. The forecasts can also be Customer specific. Forecasts can be manually entered, imported from Excel or using the “Generate Forecast” function based off of prior sales activity.
Note that Items that are Forecasted or Master Scheduled that have subordinate demand (manufacture components or kit components) will also be planned if they are MRP or DRP planned items.