This clipping mask illustrator video tutorial will show you how add a photo to your illustrator file, crop it with a clipping mask and edit the mask.
A clipping mask is a shape that you place on top of a photo or any other object in Illustrator. With the masking shape on top and the photo underneath, select both and choose Object> Clipping Mask> Make. The photo is now cropped and the masking shape is an invisible (no fill, no stroke) path on top.
The masking shape and photo will behave as a single object because they are now a clip group. To release the mask, choose Object> Clipping Mask> Release.