What's a promissory note?

[Carlos Rodrigues]

I'm taking my real estate course to get my license. And we we're spoke about promissory note. My professor summed up what it meant, and I didn't get the chance to have him clarify what it means exactly. Maybe a example would of been great. Also I've heard of people purchasing promissory notes. How is this done? And what purpose does it serve? Does it compare to a mortgage? How does it differ? Thank you in advance for your help. As I am in to the real estate industry and I'm still learning terminology. Thank you again, it's greatly appreciated!!