An initial coin offering (ICO) or initial currency offering is a type of funding using cryptocurrencies. Mostly the process is done by crowdfunding but private ICO's are becoming more common. In an ICO, a quantity of cryptocurrency is sold in the form of "tokens" ("coins") to speculators or investors, in exchange for legal tender or other cryptocurrencies such as Bitcoin or Ethereum. The tokens sold are promoted as future functional units of currency if or when the ICO's funding goal is met and the project launches. In some cases like Ethereum the tokens are required to use the system for its purposes.

An ICO can be a source of capital for startup companies. ICOs can allow startups to avoid regulatory compliance and intermediaries such as venture capitalists, banks and stock exchanges. ICOs may fall outside existing regulations, depending on the nature of the project, or be banned altogether in some jurisdictions, such as China and South Korea.

Source: WikiPedia