The type of the most derived object to which an expression refers is said to be the dynamic type of that expression. For example, if p is declared as a pointer to class B and it’s actually pointing to an object of class D (when D is derived from B), the dynamic type of the expression “*p” is “D”. References are treated similarly. For example:

   void func( B * p) // the static type of "*p" is "B"  {    D d = *p;  // however, the dynamic type of "*p" is "D"  }  int main  {    D d;    func( &d);  }

The dynamic type of an expression is determined at runtime whereas its static type is determined at compile-time.