why do downcast/ upcast java code example

Example 1: what is upcasting

Upcasting is casting a subtype to a supertype, 
going up in the inheritance tree.
It is done implicitly
 in order to use method available on any
 interface/class, the object should be of
 same class or of class implementing the interface.  
   WebDriver driver = new ChromeDriver();
or
	TakeScreenShot ts = new ChromeDriver();

Example 2: what is downcasting

Downcasting is casting to a subtype, 
going down in the inheritance tree.
It is done to access sub class features.
It has to be done manually

(TakeScreenShot)driver).takeScreenShot();