IEOs are very similar to ICOs, they have a limited number of tokens for offer, and they’ve placed limits on tokens available per user. Although ICOs tend to mint coins after the crowd sale; however, IEOs offer pre-minted tokens. Moreover, projects listed on IEOs have their tokens listed on the exchange, making it much easier for investors to invest.
Source: https://mycryptoparadise.com/what-is-an-ieo/