Virtual/pure virtual explained

Question

What exactly does it mean if a function is defined as virtual and is that the same as pure virtual?

Answer 1

A virtual function is a member function that is declared in a base class and that is redefined by derived class. Virtual function are hierarchical in order of inheritance. When a derived class does not override a virtual function, the function defined within its base class is used.

A pure virtual function is one that contains no definition relative to the base class. It has no implementation in the base class. Any derived class must override this function.