Web1 was the early stage of the Internet where few content creators existed and small personal web pages were common.
Web2 has been the dominant iteration of the Internet roughly over the past 20 years, where large companies dominate website traffic and user-generated content is abundant. The major criticism of Web2 is that large companies provide services in exchange for user data, which users have no control over.
Web3 is decentralizing the Internet, allowing its users to gain control of their data and to earn their fair share for the content they create. Web3 is composed of Dapps that run on the blockchain. You can think of Web3 as the decentralized Internet where all participants share in the value of the networks they participate in.