An initial public offering (IPO), referred to simply as an "offering" or "flotation", is when a company (called the issuer) issues common stock or shares to the public for the first time. They are often issued by smaller, younger companies seeking capital to expand, but can also be done by large privately-owned companies looking to become publicly traded.
In an IPO the issuer may obtain the assistance of an underwriting firm, which helps it determine what type of security to issue (common or preferred), best offering price and time to bring it to market.
An IPO can be a risky investment. For the individual investor it is tough to predict what the stock or shares will do on its initial day of trading and in the near future since there is often little historical data with which to analyze the company. Also, most IPOs are of companies going through a transitory growth period, and they are therefore subject to additional uncertainty regarding their future value.