We call the yeild() method it will give chance to the other thread which is in runnable state .. and our thread will also go to the runnable state...
so that the Cpu Time sheduler may choose another thread to run
or it may choose our thread too...
there is no guarantee...

When we call sleep() method it will go for waiting state
but not to the runnable state so that the Cpu sheduler will pick up another thread...