ELI5: Explain Like I'm 5

Promissory note

A promissory note is like a promise or an IOU (I Owe You). It's a written agreement between two people that says one person is going to pay money to the other. Usually, one person will lend money to the other person and make them sign the promissory note so that the other person agrees to pay the money back. Sometimes promissory notes have deadlines for when the money has to be paid back.