The Image Manager allows you to view and modify images in your account. You can change the size of your images, convert their file type, or just view them with the Image Manager.
The Thumbnailer allows you to view a small (thumbnail sized) version of any images in a directory on your site.
The Image Scaler allows you to change the size of an image on your site.
The Convert Image Format function allows you to change the format of an image to another file type. Such as changing a .jpg to a .bmp.