See ICOs as what they are trying not to be. In this case, many of these ICOs are bending over backwards to avoid being classified a security by the Howey Test, thus getting SEC attention. In this way, the company can raise money by "pre-selling" their token before the product is built. To throw a little sugar on the deal the developers also implement the ERC20 token interface so the tokens are transferable, giving rise to alt-coin FOREX-like marketplaces as tokens behave like currency.
The best analogy is if Chuck-E-Cheese pre-sold their tokens before they built their franchise location, and then people started Forex trading in anticipation of using their tokens in the future arcade. Chuck-E-Cheese uses the sale to finance the building of said franchise. Of course, this is if everything worked correctly and the owners didn't bounce to Spain with all your money, leaving you with some useless tokens.
The best analogy is if Chuck-E-Cheese pre-sold their tokens before they built their franchise location, and then people started Forex trading in anticipation of using their tokens in the future arcade. Chuck-E-Cheese uses the sale to finance the building of said franchise. Of course, this is if everything worked correctly and the owners didn't bounce to Spain with all your money, leaving you with some useless tokens.
[erc20]: https://theethereum.wiki/w/index.php/ERC20_Token_Standard