Debit Note & Credit Note

Hi Guru's,

what exactly diff between debit note and credit note? in SAP, is there any configuration? pl advice me with examples....

scenario-1: If A purchased raw material for 5000/-. user returned some raw material worth of 1000/-. in this case who will raise the note(means debit/credit) and what is the entry in SAP?

scenario-2: If B sells finished goods for 10000/-. user returned some goods worth of 2000/-. in this case who will raise the note(means debit/credit) and what is the entry in SAP?

sure i will assign points...

adv thanks