In C++, what does the keyword 'virtual' indicate?

The keyword 'virtual' in C++ is an essential feature of object-oriented programming that plays a critical role in achieving polymorphism. When a method is declared as virtual in a base class, it signals to the compiler that the method is intended to be overridden in any derived classes. This allows for dynamic binding or late binding, where the appropriate method to invoke is determined at runtime based on the type of the object being referred to, rather than the type of the reference or pointer.

For example, if you have a base class with a virtual method and a derived class that overrides that method, calling the method on a base class pointer that actually points to a derived class object will invoke the derived class's version of the method. This is crucial for achieving flexibility and extensibility in your code since it allows for defining general behavior in base classes while enabling specific implementations in derived classes.

The other options do not accurately describe the 'virtual' keyword. For instance, it does not indicate that a method can be found in any class, nor does it imply that a method is private or enable function overloading. Each of those aspects addresses different concepts in C++ programming unrelated to polymorphism and method overriding.