What is runtime polymorphism?

Answer 1

Check out this article:
http://beginnersbook.com/2013/04/runtime-compile-time-polymorphism/
in short run-time is Method Overriding as which method is called is decided during program execution. Compile time is Method overloding as which method is called is decided by the compiler based on the arguments you are calling it with. :D :D :D

Answer 2

run time polymorphism is simply method overriding, where the method is declared twice in the parent and child class. the method called in the main class will execute the method in the child class is the one executed and not that of the parent class in an inheritance structure.