An entity is a representation or model of a real world object or concept that is relevant to your application. For example, a personal finance application might use an "Account" entity to represent a bank account, or a "Withdrawal" entity to represent withdrawal of monies from a bank account.
An entity has the following elements:
This is used to identify the entity within the project. A good entity name is one that makes a connection with the real world object or concept it represents.
This is the attribute that an end user of your application should be able to identify instances of the entity by. For example, the user identifier for a "Person" entity might be the persons "Name", or their "Social Security Number". It does not necessarily have to be unique.
This is a description of the entity, and may be used to clarify the connection to real world object or concept that the entity is for.
An entity can have many attributes to describe its characteristics relevant to the application.
An entity can have many relationships to describe its real world relationships with other entities.