Aether is not a blockchain, nor is it based on one, It is a new technology purpose-built from scratch. Aether is a peer-to-peer flood network that distributes a content graph. This content graph is brought to life at every node based on that specific node’s desires. This is what allows Aether’s users to be ultimately sovereign: they have control on how this content graph is compiled into communities, threads, posts, votes, and so on.

If one would be to force the blockchain metaphor, Aether can be described as an arbitrary number of blockchains that its users select based on their interests1. The verification process happens on a per-entity basis, not on a per-block basis, therefore it can progress atomically without relying on other, possibly-not-present blockchains.

https://getaether.net/docs/faq/aether_cryptography/