Cost Center - "User responsible" and "Person responsible"

Regarding the "Cost Center" creation (using t-code KS01), I wish to understand the below points:

- What is the difference between fields "User responsible" and "Person responsible"?

- From a practical standpoint, with regards to any purchase request (for PO raised for goods purchase or "Fixed Asset" purchase) who will receive the approval request and who has the authority to approve the purchase request....