Explain what it means to have a method with a default implementation inside an interface in a programming language.

A default method inside a Java interface is a method that has an implementation within the interface itself. This allows adding new methods to interfaces without breaking existing implementations.

For example, if an interface is extended with a new method with a default implementation, existing classes automatically inherit this implementation and do not need to be changed.

Example:

public interface MyInterface {
    void existingMethod();

    default void newDefaultMethod() {
        System.out.println("This is a default method");
    }
}

Thus, default methods increase flexibility and backward compatibility of interfaces.