Web 1.0 — Host-generated content, host-generated authority. A person wanting to publish to the web had to run their own server to host a website. Websites were mainly read-only, and offered few interfaces for user content creation or interaction.
Web 2.0 — User-generated content, host-generated authority. Websites emerged that let people create user accounts so they didn’t have to host their own servers to publish to the web. This led to a lot more user-generated, interactive content, but these sites have grown to become powerful platforms, and the fact that users don’t ultimately have control over their accounts and content is becoming problematic.
Web 3.0 — User-generated content, user-generated authority. A model is emerging where people don’t have to host a server or create a user account in someone else’s database to create content. Servers can choose whether or not to host someone’s account or content, but they don’t have ultimate authority over it. The technologies that enable this are “self-certifying protocols”, based on cryptographic signatures and hashes.