The "Screen" refers to the image that appears on the monitor screen.
In the earlier games the lands are divided into areas made up individual images which fit on the screen. Sometimes areas may take up more than screen can display can be seen on the monitor screen. These are shown as a single long scrolling screens such as in QFGV, or the alleys in QFG2. Scrolling occasionally occurs in earlier games but only between two or more individual screens.
The difference between early scrolling methods and QFG5 is that in earlier games scrolling only occurs when the the Player Character reaches the edge of the screen and the next screen loads. In QFGV the camera actively tracks the player scrolling as he moves across the area.