What is the use of 'Approval Transaction Type' for Document type 'Change Order Request Requisition'

Hello,

N  : Purcahasing super user > Document Type > 'Change Order Request Requisition'

I can see different options for  'Approval Transaction Type' for Document type 'Change Order Request Requisition'

What is the use of it ?

and how can we leverage it for the benefit of our company ?

Many Thanks,

Ayesha