What is the difference between Purchasing vendor and remit to vendor. can these two be linked in Ariba OD?

1. can someone please explain these terminologies , "Purchasing Vendor" and "remit to vendor" from Ariba on-demand perspective?

2. Are Remit to Address and remit to vendor same? 

3. How to link Purchasing vendor with remit to vendor while implementing Ariba OD? what is the significance of this linking?

Thanks in advance

Regards

Mangesh