In trade allowance if you are running a promotion you might set aside some money to allocate to how much you want to spent to drive a promotion. Then measure against the amount spent vs the effective additional sales. So you can create a fund in trade allowance management which you can then assign to different trade allowance agreements.
Here is a quick overview.
D365 1611 Update5 (7.0.4475.35138)
AX2012 R3 CU11