It’s just what it sounds like: a standard way to use an Ethereum wallet that you own as an identifier across multiple services. If your first thought is, “my name isn’t even attached to my ETH wallet,” that’s exactly the point: Using a cryptographic marker as an identity means the user, not the identity provider, has total control over what information is associated with it. Eventually, you’ll be able to decide, for instance, whether a particular service needs your name, proof of your age, or a glimpse of your ETH balance. You won’t have to send all that information to every service you use.