What is a "croptool?"

The crop tool is used in the process of removing portions of an image to create focus or strengthen the composition. The crop tool allows you to select an area of an image and discard everything outside this area. The tool "trims the fat" off an image, it deletes the unwanted and keeps the desired portion of an image.

The crop tool is most commonly used in Adobe Photoshop. The tool is located third from the top in the Photoshop Toolbox, on the left side.

It's the single most powerful tool in the known universe.