The cropping tool does exactly what you would expect, it crops out a rectangular portion of your canvas and throws away the pixels outside the crop. [IMAGE]

To create a crop marquee, simply select the crop tool, click on the canvass and drag out an area.

When you do so, Photoshop will create a temporary crop selection which you can easily edit or move just like any other selection. To move the crop selection, simply position the pointer inside the area and drag. To resize, drag any of the corner points out. Drag SHIFT to scale the marquee proportionally. To rotate the selection, click drag outside the crop selection. And finally, to cancel the crop, hit the ESCAPE key.

When you are satisfied, simply click on the crop selection and it will be cropped to your specification.

Note that you can easily set, expand or contract the size of the final canvas by modifying the settings in the Cropping Tool Options Palette.