IEO is just an upgrade of the ICO projects. in previously investors bought tokens from their website and keep the token with them until tokens list on the exchange or until them returns a good profit. But the scammers and poor projects didn't reach the exchange part and investors lost their money. Now in the IEOs skip the middle part in buying tokens in the website and listing in exchange and directly sell their tokens via exchange. so we can see here same procedure happens in ICO but with the upgrade. So we can abandon ICOs for the IEOs