An IEO is launched and managed by an existing exchange to offer tokens to investors.
Initial Exchange Offering spend only centralised exchanges like Binance, FTX, Coinbase, etc. Every CEX has its own rules. Most of them don't allow conduct next investing rounds in other places.
The objective of ICOs and IEOs are essentially the same, which is to offer tokens to a large group of investors. An IEO is basically an ICO except that it is launched and managed by an existing exchange instead of the organization that created the token. The exchange holds and sells the token on behalf of the project team. This small change has significant effects on the entire process.
IEO has replaced ICO (Initial Coin Offering) as it allows solving the main problem - getting rid of fraudulent money-raising schemes. If in ICO each team, including fraudulent ones, can attract investors' funds only with the help of an advertising campaign, then in IEO it is required to pass verification from the centralized exchange (CEX), which comprehensively evaluates the project. This IEO is very similar to the listing process on a regular exchange.
However, IEOs are often criticized for the extremely biased attitude of crypto exchanges towards new projects. Often they put forward the requirement to trade only on their platform, to have a sufficiently large level of funding (even before the launch of the IEO), etc., which seriously limits many projects. Therefore, IEO has recently been replaced by Initial Dex Offering (IDO) is a new way to attract investors' money to crypto projects. The main difference from ICO is that the project is listed on a decentralized exchange (DEX).