Mode selection is a feature that allows the system to choose the best mode for an activity based on the mode priority and the available capacity of the resources. A mode is a combination of a resource and a formula that determines the duration and quantity of an activity. An operation can have multiple activities, each with multiple modes. Mode selection can be used when an operation contains several activities, each of which is assigned several modes for different resources, and the system needs to determine which resource to use for each activity. Mode selection can also be used when an activity hasseveral modes for the same resource, and the system needs to determine which formula to use for the activity. Mode selection can be performed during the planning explosion or during the interactive planning. References: Mode Selection | SAP Help Portal, Mode Selection | SAP Help Portal