Encapsulation is a fundamental concept in object-oriented programming (OOP) that involves bundling data and the methods that operate on that data within a single unit, known as a class). Encapsulation allows developers to present a consistent and usable interface that is independent of how a system is implemented internally). It also provides a public interface for interacting with the class through its instantiated objects. Encapsulation can be used to hide the values or state of a structured data object inside a class, preventing direct access to them by clients in a way that could expose hidden implementation details or violate state invariance maintained by the methods).

In summary, encapsulation is the practice of bundling related data into a structured unit, along with the methods used to work with that data, and restricting direct access to those elements. It is one of the core concepts in OOP, along with abstraction, polymorphism, and inheritance. Encapsulation provides the basic property to hide data, thereby providing security to user data.