What is Web 3.0? Here's one simple explanation...
Web3 (also known as Web 3.0[1][2][3]) is an idea for a new iteration of the World Wide Web which incorporates concepts such as decentralization, blockchain technologies, and token-based economics.[4] Some technologists and journalists have contrasted it with Web 2.0, wherein they say data and content are centralized in a small group of companies sometimes referred to as "Big Tech".[5] The term "Web3" was coined in 2014 by Ethereum co-founder Gavin Wood, and the idea gained interest in 2021 from cryptocurrency enthusiasts, large technology companies, and venture capital firms.
Source: https://en.wikipedia.org/wiki/Web3

Here's a good video contrasting Web 1.0, Web 2.0, and Web 3.0.