Not all recommendations provided by the system will make sense - the system may not have an important piece of information, like an upcoming special event. Or the order may make sense, but it can't be implemented, because there are factors like quotas that prevent your orders the quantity you want.
In those situations, it will be annoying if the system keeps making the same unwanted recommendation, and you have two options:
Muting Recommendations: The recommendation will be removed from the list, and the system will not mention them again for a certain time or even indefinitely.
Discarding Recommendations: The recommendation will be removed from the list for now, but during the next recommendation run, it will come up again.
Note that Muting and Discarding actually place in Replenishment Recommendations. In this section, you can view what was muted/discarded, and cancel these actions if they are no longer applicable or were applied in error.