Accounts receivable: these are amounts owed to you on account. Your provide others with a service or goods. You send them invoices. Until you are paid, these are accounts receivable. In business terms, these are simply amounts owed to you from your customers under normal trade terms.
Accounts payable: you receive an invoice from someone for goods or services on account. Until you pay the invoice, these are accounts payable. In business terms, these are simply amounts you owe to your suppliers under normal trade terms.
Notes receivable: are debts owed to you under a written promise (often called a promissory note or a loan agreement).
Notes payable: likewise, are debts you owe under a written promise.
Notes payable and receivable are usually stated separately from loans secured by a mortgage or deed of trust.
CUSIP numberHey, Fred! I will send you an invoice for $100 for this answer. This will be an account receivable for me, and an account payable for you.
Can't pay right now? That's OK! I will lend you the money and you can pay it back over time. Now I have a note receivable and you have a note payable.
Say what? You would rather give me stock in your American company, Puli USA, Inc.? OK, that works for me. The stock certificate will have a unique CUSIP number on it.