An electronic representation of an entity used by information systems to uniquely identify the agents with which they interact.
Digital identities may used by three types of entities: people, organisations, and devices.(1)
To function as a digital identity, the uniqueness of the information that represents a party is established within a set of identities. The information in a digital identity need only be unique within the domain of other identities with which it may be compared.
For example, social security numbers issued by the United States of America can be used to uniquely select (or identify) the people they represent, but only from the set of people who are legally recognised citizens of the U.S.A.
Digital identities are related but different to accounts and credentials. In general conversation these terms may be used synonymously, and credentials may be a subset of the data in a digital identity. Nonetheless the purpose of a digital identity is to identify the entity it represents, while the purpose of credentials is to provide evidence that a digital identity is being asserted by the correct entity during an access transaction. Accounts on the other hand define the relationship between an identity holder and a service provider.
(1) Device here refers to either physical and software entities.