Interview Question for Senior Software Engineer at Intuit:

Using virtual destructors, you can destroy objects without knowing their type - the correct destructor for the object is invoked using the virtual function mechanism. Note that destructors can also be declared as pure virtual functions for abstract classes.

If someone will derive from your class, and if someone will say "new Derived", where "Derived" is derived from your class, and if someone will say delete p, where the actual object's type is "Derived" but the pointer p's type is your class.