Infinite planning is a method of material requirements planning (MRP) that creates new orders without checking the capacity availability of the work centers. This means that the capacity requirements of a new order are created regardless of the existing capacity load or constraints of the work center. Infinite planning assumes that the required capacity can be increased or adjusted as needed. Infinite planning is suitable for situations where the capacity supply is flexible and the demand is urgent or unpredictable. However, infinite planning can also result in capacity overloads or unrealistic schedules that need to be resolved later by capacity leveling or rescheduling. Reference: SAP S/4HANA Production Planning and Manufacturing II, Unit 1: Material Requirements Planning; [SAP S/4HANA Production Planning and Manufacturing Certification Guide], page 77.

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 has several 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. Reference: Mode Selection | SAP Help Portal, Mode Selection | SAP Help Portal