Software Architect's Handbook

Entities

Entities are objects that are defined by their identity and not their attributes. They are mutable because the values of their attributes can change without changing their identity. If two objects have the same values for their attributes, other than their unique identifier, they are not considered equal.

For example, if you had two Person objects with the same first and last name values for those corresponding attributes, they are still two different objects because they have different identities. This also means that a value for an attribute such as last name can be changed on a Person object and it still represents the same person.