The Action and Cut buttons are to start and stop continuous or long term action if that is the nature of the display output. The Near button decreases the boundary limits of the displayed area by 10% with each click. The Far button has the opposite effect. The Left, Right, Up and Down buttons shift the viewing area in their respective directions by one area width or height as appropriate. The Reset button restores the initial values of the viwewing area boundary limits. The limits are displayed at the ends of the viewing area in the left and bottom margins. The limits appear in text input boxes so that you may enter a specific value for any of the limits, upper or lower x and upper or lower y.
In this example all the action button does is repeatedly plot a sine curve of amplitude 10 units, along the x-axis from the x low limit to the x high limit. Go ahead and experiment with the controls so you see how they work. If in scrolling the applet window, it does not paint completely, just click on the Reset button to clean up the picture. Notice that the limits do not have specific units attached to them. They might be in meters, miles or minutes. You need to be aware of the units represented by each axis of the display area.