The web originally required technical skills to publish anything to it. Retrospectively, this stage has been called Web 1. Then came Web 2 (aka the social web, the ‘read + write’ web), enabling anyone anywhere to publish anything.
A vision for the web known as the semantic web (or semweb for short) was and is still referred to as Web 3. Confusingly then, the recent application of novel cryptographic techniques to the challenges of distributed computing has also attracted the moniker.
Ironically for a field obsessed with distributed consensus, there is no consensus on the definition of this Web 3, and so the description in the previous sentence will suffice here.