This is a term that is used to describe the combination of Web 2.0 and Web 3.0.
Web 2.0 is the Internet as we know it. It is a siloed system controlled by major technology corporations who each have their platforms that are closed ecosystems. The front end(s) tie into a back end server system that is controlled by company.
Under this scenario, there is no account ownership by the individual user. They are fully under the control of the corporation. At the same time, all data, along the rights, is owned by the entity which is selling it. We all know the revenues that are generated by from this resource.
The key concept is centralization.
Web 3.0 offers true account ownership. It incorporates blockchain which is distributed ledger technology. Introduced by Bitcoin, this is a ledger of financial transactions similar to what a bank does. However, future iterations along with technological development allowed for the entry into fields such as social media turned these into decentralized databases.
Since they are permissionless, public blockchains, anyone can create a front end that pulls the data from on-chain. The node system is decentralized in that the block producers are unrelated. Here we see the result of having an immutable database where access is done through private keys that are tied to the wallets.
Web 3.0 also offers the ability to incentivize different activities through the use of cryptocurrency. This applies to both infrastructure along with social media applications.
The key here is decentralization.
One of the benefits is that the different applications connected to a blockchain such as Hive all have the same log in. Hence, one account applies to all. When it comes to content creators this is important since one's following is at the base layer, not resident to the website or platform.
Web 2.5
This is a rather "tongue-in-cheek" label that is placed upon many projects.
The idea of Web 2.5 is that a project seeks to separate itself from the traditional structure. In other words, the claim is that it is moving away from Web 2.0. The challenge is that while it will espouse the tenets of Web 3.0, the structure is not aligned with that.
One of the biggest downfalls is these all tend to be built on centralized infrastructure. This means that it is really a traditional server/front end system that is controlled by an individual or related group.
This brings up one of the largest issues: censorship resistance.
If the data is housed in a manner where it is controlled, that means it can be deleted. When this ties into the account management system, that means the person's digital life can disappear. This is no different than getting banned on Twitter or Facebook.
With Web 3.0, it is impossible to ban someone or close their account. The management system is coded into the blockchain, meaning the software is run on unrelated computers all over the world.
This is what Web 2.5 tries to promote yet fails in the way it is structured.
Much of this is the typical money grab by well known individuals. They use their notoriety to attract venture capital (VC) funding. This presents an issue from the start since, historically, VC funded ventures always pit the userbase against the VC firm. At some point, the latter wants to be paid, something that ends up being a detriment to the user experience.