Adding Pizazz to That Plain Object
According to Weinmann and Lourekas, "a gradient fill is a gradual blend between two or more colors." In other words, it's like a rainbow with as many colors as you chose and in the order you want. All three of the following circles have been filled with gradients.
To fill an object with a gradient, you must first select the object, then select the Gradient button at the very bottom of the toolbox (you can also just hit the period key). When you do so, your object should be filled with the default gradient. Using the Color and Gradient palettes, you can alter the gradient any way you wish.
In this case, I have added colors to the gradient by clicking just below the gradient sliderthe bar with the gradient shown on it. Once you have the number of colors that you want, you can click on any color box, below the slider, and move it as needed or change the color in the Color palette until you obtain the gradient you want. The diamonds above the bar determine how much of a color there is on either side of the transition, and the Type can be either radial or linear to create either a circular or straight gradient.