The Eyedropper tool sets the fill options of the selected objects to match the color, pattern or gradient fill of whatever it clicks on.
If you click on a bitmap, the eyedropper will return a solid color that matches the pixel you clicked on.
Working with Color
Using the Eyedropper
Selecting a Solid Fill from a Gradient or Pattern
Setting Stroke Colors with the Eyedropper
Adding a Fill Selected with the Eyedropper to a Swatch Table
Available Color Models
Working with Swatch Tables
Applying Colors Using the Color Mixer
Defining Colors Using the Color Specs Dialog Box
Setting the Default Fill / Stroke Color
Setting the Background / Foreground Color
Creating Test Swatches