The time line is mainly used for animating. It works by using key frames and then blender will work out whats in between.
You will not use the blender time line until you learn many of the basics but it is still quite simply. To add a key frame you press I and to remove a key frame you press Alt I. You can play the animation by pressing the play button.
The start number shows you when you animation will start when you Render it and the End number tells you how long your animation will last.
The time tine is an important tool in blender as without it we would not be able to make animations.
Another cool tool of the time line is the record button (the red one). This allows you record the movement of an object in real time. All you have to do is turn on the record button and press play. Then you can move your object and it will record its movement.