You can switch to a different page by clicking on it within this button, or by holding down the control key and typing one of the arrow keys. The program xload is running in this button. It shows the load of the computer relative to time. Clicking on this button will launch top in a xterm window. A window can be thought of as a container for a program.
All windows have the same basic look and feel, regardless of their contents.
To make a window active, simply drag the mouse into that window. There can only be one active window at a time. You can use this to scroll back and forth to view the window contents. Clicking on the title bar of a window will bring it to the front, or if it is already in front, send it to the back. To resize a window, click and drag in the lower left or lower right hand corners with the left mouse button.