How does an interface differ from an abstract class?

An interface primarily serves to define a contract for classes that implement it, specifying what methods must be present without providing any implementation for those methods. This means that any class that implements an interface is required to provide concrete implementations for all of the methods declared in that interface.

This key characteristic of interfaces emphasizes their role in establishing a clear boundary of expected behavior, facilitating polymorphism and allowing for loose coupling in a system. In contrast, an abstract class can include both abstract methods (which have no implementation) and concrete methods (which do have implementation). Thus, while both abstract classes and interfaces can be used to achieve abstraction, interfaces are specifically designed to only declare methods without any implementation, reinforcing their contract-like nature.

The other options reflect concepts that do not accurately differentiate interfaces from abstract classes. For example, while an abstract class cannot be instantiated, this statement applies equally to interfaces in terms of direct instantiation. However, interfaces are focused on the contract aspect, hence option B encapsulates the core distinction effectively. Additionally, terms like method overloading do not specifically relate to the fundamental differences between interfaces and abstract classes, where the focus is primarily on their roles in defining behavior rather than how methods are defined.