In Premiere Pro and Premiere Elements, the work area defines a portion of the timeline for preview purposes. Hitting the enter key activates playback from the beginning of the work area bar to the end. Any rendering necessary to play that segment is also performed.
There are several ways to set the work area bar. The most cumbersome is to drag both the in and out point of that bar to the desired location. The fast and easy way is to place the CTI at the desired start of your work area and press "Alt" + "[". And you guessed it, to set the end point of the work area, press"Alt" + "]".
You can set also the work area bar by zooming into to the desired view of the timeline and then double-click the work area bar. The bar will automatically fill the current view of the timeline.