All three are public token sales. What separates them is who stands between the project and the buyer, and that has consequences for what is checked before money moves and who has anything to lose if the project fails.
The initial coin offering, which dominated 2017, was direct: a project published an address, buyers sent funds to it, and tokens were distributed later. There was no intermediary, no vetting, and in most cases no legal structure. Enormous sums were raised on whitepapers alone. The model collapsed under two pressures — a failure rate that became impossible to ignore, and enforcement action by securities regulators, most consequentially in the United States, where the analysis was that many of these sales were investment contracts and had been offered without registration or exemption.
The initial exchange offering placed a centralised exchange in the middle. The exchange conducted the sale on its own platform, applied identity checks, and staked its reputation on the projects it hosted. Buyers got a measure of screening and a listing on completion. The weakness was the incentive: an exchange earns fees from listing and from the trading that follows, which is not an alignment that produces conservative vetting. Some venues screened seriously; others did not, and the label alone said nothing about which.
The initial DEX offering removed the intermediary again, selling through a decentralised exchange or a launchpad contract. Anyone can launch one, permissionlessly and immediately. That openness is the model's point and its problem: there is no gatekeeper at all, sales can be created in minutes, and the format is the natural home of the launch-and-abandon token. It is also where bots are most effective, front-running public buyers into a new pool within the same block.
The common risks run across all three. Buyers are early, which means illiquid and heavily exposed to the vesting schedule of everyone who bought earlier still. The token usually does not exist as a working product at the time of sale. Allocation terms for private rounds are often materially better than the public terms and are not always disclosed clearly. And the regulatory position of any given sale depends on jurisdiction, on structure, and increasingly on the specific rules a jurisdiction has since written for public offers of crypto-assets.
The practical reading is that the format tells you almost nothing about quality, and the checks that matter are the same in all three cases: what the token does, who holds it, what unlocks when, and whether the sale is being offered lawfully where you live. A venue's brand is not a substitute for any of them.