What is the difference between Weighted Historical Index with Source Data and the Import Forecast creation methods in short-term forecasting?

While both of these creation method options allow you to import a file, the functionality is completely different. 

• Weighted Historical Index with Source Data Import creation method allows you to import up to 8 weeks of historical data to be used to create a Weighted Historical Index forecast up to 1 week long. Note: This used to be called “Import data” in previous versions of workforce management.
• The Import Short-Term Interval Forecast creation method does not import historical data, it actually imports a final forecast that was created outside of workforce management that is from 1-6 weeks long. Please note that some users will generate a forecast using Automatic Best Method Selection in workforce management and then export it and edit it in another application like excel.  The Import Forecast option allows you to import this edited forecast as a new forecast in workforce management.