A look at ICOs, IEOs, and IDOs:
Ethereum launched its public crowdfunding campaign in July 2014, with participants using Bitcoin to buy ETH.
The key difference is who organizes the sale: with an ICO, the project sells directly; an IEO is vetted by an exchange; and an IDO takes place on-chain.
$ETH 2420.05(+4.03%)

Do your own research before investing.