The Preview window is directly related to the Timeline and displays the video content presented in the Timeline. The seek slider in the Timeline is used to seek the preview to any position on the Timeline. The preview is used to see how your composition on the Timeline is shaping up.
The Preview window can be further divided into several elements.
This is where the video content in the Timeline is actually displayed. The size of the window can be altered by selecting the project dimensions when creating a new project.
You can also preview the Timeline in full screen. Select Full Screen Preview from the View menu or press Ctrl+Q to switch to full screen mode. To switch back to normal mode press Alt+Tab.
The preview controls enable you to Play, Stop, Pause, Forward and Rewind the preview. The Previous Frame and Next Frame button allow you to see the view frame by frame. These controls behave similar to controls in any media player.
Volume of the preview can be changed by clicking the volume button. Change the volume from the drop down that appears.
The preview display on the bottom right of preview window shows the current slider position in the Timeline and the total duration of the Timeline. The reading on the left of the slash shows the current slider position and the reading on the right side of the slash displays the total Timeline duration. The time for both the readings is expressed in "Hours:Minutes:Seconds:Milliseconds".
The Seek Bar is used to see the preview of any part of the video composition. In addition to the seek slider in the Timeline, this seek bar in on the preview window can also be used.
If you click on the Repeat button placed right after the seek bar, the preview keeps playing your Timeline over and over again. After the entire duration of the Timeline has been played, the Preview starts again (instead of stopping like it normally does) and keeps going on endlessly until you click the Repeat button again to stop it.