1) What is Thread in java? Threads consumes CPU in best possible manner, hence enables multi processing. Multi threading reduces idle time of CPU which improves performance of application. Thread are light weight process. It belongs to java.lang package. It can run mutiple threads simutaneously . 2) How to implements threads in java? By implementing java.lang.Runnable interface or extending java.lang.Thread class and then extending run method. Thread creation by implementing java.lang.Runnable interface. And then create Thread object by calling constructor and passing reference of Runnable interface i.e. runnable object Thread thread = new Thread(runnable); 3) We should implement Runnable interface or extend Thread class. What are differences between implementing Runnable and extending Thread? you must extend Thread only when you are look