Set and Vector

<Set>
1. more efficient to add and move objects from the set.
2. keep all the elements in order by itself.
3. No duplicate elements.

<Vector>
 1. more time is required to add and move.
2. keep elements in the order you inserted them.
3. Possible to have duplicated elements.

When inherited from a class with virtual methods, those virtual method are not inherited automatically; you still need to declare virtual methods in the child classes.