It touches on the topic of downcasting (cast a derived class to its base class)
First of all, downcasting itself is usually unnecessary in most situation where the virtual functions are suffice.
If it must be done, use dynamic_cast. It will return null if cast is unsuccessful
RTB stands for “Real-Time Bidding”
Virtual functions are dynamically bound, but default parameters are statically bound
Lead to difference in behavior if a derived class is casted to its base class. Not advised.
The purpose of declaring a _pure virtual function_ is to have derived classes inherit a function interface only
The purpose of declaring a simple _virtual function_ is to have derived classes inherit a function interface as well as a default implementation.
The purpose of declaring a _nonvirtual function_ is to have derived classes inherit a function interface as well as a mandatory implementation.