HYIP operators generally set up a website offering an "investment program" with returns as high as 45% per month or 6% a day that discloses little or no detail about the underlying management, location, or other aspects of how money is to be invested because no money is invested. They often use vague explanations, asserting little more than that they do different types of trading on various stock markets or exchanges to generate the returns they purport. The U.S. Securities and Exchange Commission (SEC) has said the following on the matter: "These fraudulent schemes involve the purported issuance, trading, or use of so-called 'prime' bank, 'prime' European bank or 'prime' world bank financial instruments, or other 'high yield investment programs.' ('HYIP's) The fraud artists... seek to mislead investors by suggesting that well regarded and financially sound institutions participate in these bogus programs."
A high-yield investment program (HYIP) is a type of Ponzi scheme, which is an investment scam that promises an unsustainably high return on investment by paying previous investors with the money invested by newcomers.
A Ponzi scheme is a fraudulent investment operation that pays returns to separate investors from their own money, paid by subsequent investors, rather than from any actual profit earned. The Ponzi scheme usually entices new investors by offering return other investments cannot guarantee, in the form of short-term returns that are either abnormally high or unusually consistent. The perpetuation of the returns that a Ponzi scheme advertises and pays requires an ever-increasing flow of money from investors to keep the scheme going.
http://en.wikipedia.org/wiki/HYIP