In short, Ethereum Name Service is like a .com domain, for use on the Ethereum network. That said however, ENS has more functionality than a standard Web2 domain, and further functionality is being built into the technology.
Started at the Ethereum Foundation in early 2017, ENS is a public good, a basic piece of Internet infrastructure that belongs to the community. Anyone and everyone is free to interact with the protocol as they are permissionless contracts on the Ethereum blockchain.
ENS Website
ENS is a part of Ethereum. That makes it easy to trust, and makes it relevant as an asset. A bet on ENS is a bet on the Ethereum network, and plenty of smart people are betting on the Ethereum network at the moment.
So what can I do with my ENS domain? Well for starters, ENS domains can be set as the primary address for an ETH account. This functionality removes the need for messy cryptographic hashes as wallet addresses, which are a nightmare if they cannot be copied and pasted for whatever reason. ENS makes it so much easier, just mint your domain name of choice, say DomainName.eth, set that as the primary address for the account, and all future tranactions can be sent to DomainName.eth. It makes life easier.
Of course where this gets really interesting when we consider it speculatively. What I mean by that is when we consider how much stock people will place in having a premium ENS name in ten years say, if the technology does win out. What will YourFirstName.eth be worth, and will you own it, or will someone else? It is for this reason that seemingly strange things are doing well, such as three digit ENS names. Ask yourself honestly though what do you think 001.eth will be worth in ten years time.
I should add at this point that there are caveats with minting ENS domains, namely that 3 characters is the minimum, and that there is a premium to be paid for registration of 3 and 4 character domains. 3 character domains cost $640 per year for renewal, while 4 character domains cost $160 for renewal. Larger domains only cost $5 annually. This is an important point to keep in mind if you are considering stacking ENS domains.
One future functionality that is in the works for ENS domains is the addition of subdomains, and its exciting. I have heard it said it will be possible give away or even rent out subdomains if you are the domain owner. The owner of Club.eth, can create and distribute Member1.Club.eth, Member2.Club.eth, etc. and this opens up a whole world of possibilities for use of subdomains in conjunction with projects, as well as their use as a method to generate passive income. By now you should be beginning to see why Loan.eth, Rent.eth, Nike.eth, etc. are potentially so valuable.
Of course it is early days and the survival of Ethereum is not 100% guaranteed at this point, but that is one of the perils of being early. This is a fledgling technology and it means that there is risk but it also means that there are tonnes of cool names out there that have not been minted yet. Imaginative people will find many cool names that have been overlooked because we are just that early, and that is part of what makes ENS domains such a fun investment.
ENS domains can be minted at the top of the page, and there is also a link to ENS Vision , a website that has been created especially for ENS domains, by a team that just keeps delivering. The site is quickly becoming a one stop shop for ENS and has some cool features like clubs, bulk registration and a handy sweeping tool. ENS can be bought on Opensea also but ENS Vision would be my site of choice.