Is there a term for a fund that takes money from people (let's call them "investors"), promises to pay them back that money plus abundant interest in the future

Is there a term for a fund that takes money from people (let's call them "investors"), promises to pay them back that money plus abundant interest in the future, and doesn't actually have enough (or any) money to pay all of these "investors", so it resorts to borrowing money to keep payments going a little longer?