Transformations : Dilations
First try the Dilate slider to get a simple visual idea that dilating is about growing in scale (doubling, tripling, quadrupling, etc).
To shrink, go less than 1. Half size would be 0.5. Watch what happens when you go into a negative dilation.
Just for reference, to create a dilation like this, you would want to place the centerpoint of your dilation at the midpoint of the base of the object.
To better understand how to solve typical math problems which will have you dilate with the centerpoint at the origin (0,0), you should use the other slider DilateAboutOrigin.