What is a Thread?
        
        
 
   
   
   
   
-  A thread is a single sequential flow of control within a 
        process.
   
   
 -  Each Java program normally consists of multiple threads that share
        the CPU according to some scheduling algorithm (normally depending
        on the operating system).
   
   
 -  From JDK, the relevant components are (1) the interface Runnable
        and (2) the class Thread