ICOs are they were known, mimicked IPOs from traditional finance, selling new coins to backers who subscribed to the offering.
Similar to an initial public offering, an initial coin offering is when a new project offers its cryptocurrency to the public for the first time in order to raise funds for further development.
However, buying in at an IPO gives you actual ownership, since you own stocks, but there is no ownership involved in ICO tokens. Typically investors speculate on the success of the blockchain in the future for their return on investment.
ICOs were exceedingly popular during the crypto bull run of 2017, but have since become controversial due to legal issues and downright scams.