Add Resize - Resize an image to an exact set of dimensions, ignoring aspect ratio.
Add Rotate - Rotate an image.
Add Scale - Resize an image maintaining the original aspect-ratio (only one value necessary).
Add Scale And Crop - Resize an image to an exact set of dimensions, ignoring aspect ratio.
That's what i get when editing preset (…/admin/build/imagecache/ID). I think description for Scale & Crop is just copy&paste from Resize. This has to be change according to fact that Scale maintains original aspect ratio.