Ethereum Name Service
ENS published an explainer on how ENSv2 makes the hierarchy of names explicit onchain. Instead of every name living in one flat registry, each name can define its own registry, resolver, and rules for the namespace below it. The post points to more detail on the ENSv2 architecture as the revamped naming layer moves toward mainnet.

Ethereum Name Service
The Ethereum Name Service (ENS) is a distributed, open, and extensible naming system based on the Ethereum blockchain.
ENS’s job is to map human-readable names like ‘alice.eth’ to machine-readable identifiers such as Ethereum addresses, other cryptocurrency addresses, content hashes, and metadata. ENS also supports ‘reverse resolution’, making it possible to associate metadata such as canonical names or interface descriptions with Ethereum addresses.
ENS has similar goals to DNS, the Internet’s Domain Name Service, but has significantly different architecture due to the capabilities and constraints provided by the Ethereum blockchain. Like DNS, ENS operates on a system of dot-separated hierarchical names called domains, with the owner of a domain having full control over subdomains.
Top-level domains, like ‘.eth’ and ‘.test’, are owned by smart contracts called registrars, which specify rules governing the allocation of their subdomains. Anyone may, by following the rules imposed by these registrar contracts, obtain ownership of a domain for their own use. ENS also supports importing in DNS names already owned by the user for use on ENS.