Entity: This is the core concept in the Entity Framework. An Entity essentially models individual objects, like, employees, customers, etc. It is something that is uniquely definable, distinctly identifiable, and contains information pertaining to the entity.
Relational or Logical Model: A relational or logical model depicts the logical view of data that comprises of the normalized entities and their inter-relationships in a database.
Object Model: An Object Model may be defined as a collection of the objects, members, and properties of a class and the relationships between them that illustrates the structure of a system. An Object Model of a system is centered on the three basic properties of Object Oriented Programming—encapsulation, abstraction, and inheritance.
The Entity Data Model (EDM) is an implementation for the Entity Relationship model (commonly called the E-R model). It depicts the entities and their relationships. The EDM is a view of the data store that your application will use.