In short, (runtime) polymorphism is a tool that allows us to write code that is better decoupled - the code that decides which method to call when can be different from the code that decides which implementation to use for that method call.
The soul is dyed the color of its thoughts. Think only on those things that are in line with your principles and can bear the light of day. The content of your character is your choice. Day by day, what you do is who you become. Your integrity is your destiny - it is the light that guides your way. - Heraclitus