web1 -> peer-to-peer decentralized networks without built-in consensus or economics; end up de facto centralized because of this
web2 -> corporate owned networks; from iMessage to Tiktok to Reddit, this is most major networks today
web3 -> networks whose decentralization is enforced by cryptography and economics; Ethereum being one such example of a programmable network
If the terms were just marketing that would be one thing. But they actually describe real differences in properties that have significant consequences for those who build and rely on them.