To access Territory Target Variance Based On Item Group go to

Sales > Performance > Sales Reports > Territory Target Variance Based On Item Group

This report will provide you variance between target and actual performance of Sales in particular territory. This report is based on Sales Order report. Though Sales Person is defined in the Territory master, its details are not pulled in the report.

Note that the Territory of the Customer/Customers must be set accordingly for this report to work. For example, in the following screenshot, the target was approx eight units and five was achieved, hence the variance is three.