In object-oriented programming, what does 'inheritance' refer to?

Inheritance in object-oriented programming is a fundamental concept that allows a new class to inherit properties and behaviors (methods) from an existing class. This mechanism facilitates code reusability and establishes a hierarchical relationship between classes. When a class derives from another, it can access the parent class's attributes and methods while also having the ability to add new attributes or override existing methods, thus promoting an organized structure in code development.

This characteristic of inheritance enables developers to create more abstract code, reducing redundancy and enhancing maintainability. It allows subclasses to leverage the common functionality of a superclass while implementing their specific features. For example, if you have a base class called "Vehicle" with methods and properties related to vehicles, a subclass like "Car" can inherit from "Vehicle" and add specific attributes such as "number of doors" without rewriting the entire set of vehicle functions.

The other options do not capture the essence of inheritance in the context of object-oriented programming. Duplicating data refers to a different concept, and encapsulating functions mainly relates to the idea of bundling data and methods together. Optimizing performance is also not directly linked to the concept of inheritance but rather concerns efficiency in code execution.