It is often the case that you would like a program to be able to do more than one thing at a time. You might, for example, want to monitor the keyboard for a key being pressed by a user and, at the same time, track the movement of the mouse by the user and repaint the screen. Each of these tasks can be thought of as a single thread in a program. These threads all exist in the same executing environment and so are not the same as different programs. They are separate activities within a program, each of which has a beginning and an end. So far, all of the programs that you have written have had only one thread in them and this has been the thread started by the main method. So in Unit 7 for example, in the ball and paddle game, the control of the paddle and the movement of the ball were competing for the computer's resources and this gave the game a jerky action. What we would really have liked to do is have the paddle control and the ball motion working independently of each other. We can achieve this by making each of these tasks into a thread. Each of these threads can then be running simultaneously, each being between their start and finish at any point in time. Threads are not the actual static code itself but rather they are the dynamic process of executing that code.