When do I use valid for „Segment Member Relationships“ under Segmentation Basis?

Dear experts,

can anyone please explain the difference between valid for 'segment members" and valid for "segment member relationships" and give me an example when the use of "segment member relationships" would be recommendable?

I created two segmentation basis - B2B and B2C. Does it make sense here at all?

Any explanation would be highly appreciated.

Best regards,

Janine