What is the difference between credit note and debit note?

• When a buyer returns goods to the seller, he sends a debit note as an intimation to the seller of the amount, quantity being returned and requesting return of money. 
• Sent to inform about the debit made in the account of the seller along with the reasons mentioned in it
• Purchase returns book is updated on the basis of the debit note
• Often used to return  goods on credit
• Sales returns a/c Debit and Credit to Debtors a/c

• When a seller received goods (returned) from the buser, he prepares and sends a credit note as an intimation to the buyer showing that the money for the related goods is being returned in the form of a credit note.  
• Sent to inform about the credit made in the account of the buyer along with the reasons mentioned in it
• Sales return book is updated on the basis of credit notE
• Journal entry to record a credit note is Creditor's a/c debit and credit to Goods returned a/c.

a Credit note allows a buyer to purchase in a future price, or if the seller is a bank it might indicate a mistake being fixed, or various situations. 

When the opposite event happen it is called a debit note.