A thread is a thread of execution in a program. The Java
Virtual Machine allows an application to have multiple threads of
execution running concurrently.
When a Java Virtual Machine starts up, there is usually a single
non-daemon thread (which typically calls the method named
main of some designated class.
We can create a thread extending a Thread class as shown in below image.
in above image we have create a thread by extending a Thread class and we are executing the thread's task
by instantiating a new thread and starting it using start() method of Thread class at circle 1.