HOW TO CROP in PHOTOSHOP CS?

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I have a question that I can’t seem to find the answer for anywhere. It’s hard to explain. Maybe it is not possible. But how do you crop something to a custom drawn selection? *I am not just talking about the type of cropping that you turn the path into a selection and then invert the selection and hit delete. This still leaves white space around your selection while the picture is still in a rectangular shape. I am talking about so that the actual picture file is in the shape of your path… Anyone?