Traditionally, IPOs occur with companies that have been in business for a significant amount of time. ICOs are popular with start-ups who need to raise capital to get their project off the ground. Their whitepaper is the document which gives investors an idea and viability of their product.
A fundamental difference between an IPO (Initial Public Offering) and an ICO (Initial Coin Offering) is what the investor gets out of it. The more traditional IPO allows investors an equity share or some stake in how the organisation runs. ICOs on the other hand will give its investors tokens which come with the assurance that the value of the token will grow and the investor will profit accordingly.