A historical report can help the sales manager monitor the team's sales pipeline to make sure they meet the current and future sales goals. You'll probably want to compare historical and current values of key attributes of opportunities that have changed over time, such as amounts and status of your team pipeline.

Historical trend reports offer this capability without any special additional permission for the user to run the historical trending report. However, the admin needs to configure the objects and fields enabled for historical trending.

The same applies to field history; the historical trend will not track the fields until you enable historical trending for the object.