A Plain Old CLR Objects (POCO) is a class, which doesn't depend on any framework-specific base class. ... These POCO entities (also known as persistence-ignorant objects) support most of the same LINQ queries as Entity Object derived entities.

POCO class is the class created as extension for the class created from the ef. let's assume that we have class students generated from the ef and we set our annotations then we recreate the model all annotations will be lost the the solution is POCO class