Identity
From Organic Design wiki
In short, a DID is an address on the internet that someone called a subject (you, a company, a device) can "own" and control directly, like a username but randomly generated. It can be used to find a connected DID document which is like a business card, providing extra information for finding or contacting or checking the signatures of that subject; that subject can update or remove that listing over time, directly.
Strictly speaking, a DID is a string that functions as an address. Sometimes people might use the term to refer both to the DID and the DID Document, When you use a DID Method to resolve the DID you get the associated DID Document. A DID without a DID Document is like a dead end!