A more thorough explanation:

A Ponzi scheme is a type of investment scam named after Charles Ponzi, who defrauded investors out of millions of dollars in the 1920s. In a Ponzi scheme, investors are promised abnormally high returns that are actually paid from money contributed by newer investors. The scheme depends on the recruitment of new investors to pay high returns to older investors, much like a pyramid scheme. However, the returns are not from legitimate investments, but are merely a transfer of money from new investors to earlier investors.

Some characteristics of Ponzi schemes include:

• promises of high returns with little or no risk
• unclear investments about which there is limited information
• restricted access to assets

For example, a Ponzi scheme operator may promise investors a 20% return on their investment in just one month, with no risk involved. The operator may claim to be investing in a new and innovative technology, but provide little information about the technology or the company behind it. When investors try to withdraw their money, they may be told that their funds are tied up in the investment and cannot be accessed for a certain period of time.

One of the most well-known Ponzi schemes was carried out by Bernie Madoff, who was sentenced to 150 years in prison in 2009. Madoff's scheme involved using new investors' money to pay off earlier investors, while claiming to be investing in stocks and other securities. However, in reality, Madoff was not investing the money at all, but simply using it to pay off earlier investors and fund his own lavish lifestyle.

It's important for investors to be cautious and do their research before investing in any opportunity that seems too good to be true. If an investment promises high returns with little or no risk, and the details of the investment are unclear or difficult to obtain, it may be a Ponzi scheme.