Make sure the Transparency Window is in the palette on the right hand side (Window/Transparency)
Make a background shape (a blue rectangle in this case)
Put in some artwork (a picture from Alaska)
Put in an Opacity Mask Object (a smaller rectangle)
Give it a gradient fill (black and white)
Click on the Gradient icon and you can draw your own gradient or use the Gradient Palette to make changes
Select both the Mask Object and Artwork (Shift Click)
Go to the menu on the Transparency palette and click Make Opacity Mask
Make sure Thumbnails show on Transparency Menu
Go to gradient panel and change to Radial - change back
Add Effects to Opacity Mask - Effects/Blur/Gausian Blur (to create a feathered look)
Resize Opacity Mask
Rotate Opacity Mask
Click on artwork thumbnail, click on link between thumbnails to release lock, move artwork or mask around.
Try and recreate this image using Adobe Illustrator
Two Opacity Masks were used.
One for the color of the "M" (which was a clipping mask as well)
A 2nd Opacity Mask for the "M" and the leaf.
To place a gradient on an Letter - Type the letter, select it with the selection tool,
click on the graphic style palette, and select a gradient. You can now alter the gradient.
My "M" has a stroke on it as well.
To change to the color of the "aple", you first need to create an outline for the letters and ungroup them.