Basically, the HYIP owner calls his or her program a "ponzi-structured game" where one should "not invest money one cannot afford to lose", and where there is "never a guarantee of earnings or refunds".
They promise to pay out up to (e.g.) 95% of deposits, the rest going to hosting or other fees and the admin's profit. The first investors will make a handsome profit and are encouraged to refer other people to the program by referral commission, the fact that they have already made back their principal and are playing with profit, and that the more people who deposit money, the more money can be paid out to investors.
Strategies can be developed to maximize profit using these games.
This may help out some of those that may be new to the HYIP scene, and it may help others create some interesting strategies. Please note that I am not the author of this material.
This was found at http://en.wikipedia.org