Pillow, a "friendly fork" of the original Python Image Library (PIL), is a widely-used tool for 2-D image processing in Python, offering functionalities such as opening, resizing, and saving images. Its compatibility with older PIL makes it a versatile choice for image manipulation across multiple platforms. The tutorial highlights the use of Pillow to perform basic tasks like opening an image, checking its attributes, and saving it in different formats, as well as resizing it with the resize() and thumbnail() functions, the latter preserving the aspect ratio. Additionally, it covers pasting images for watermarking, including using transparency masks to ensure seamless integration of logos onto images. Advanced users can explore further capabilities such as adding alpha layers or converting images to different color formats, with the documentation serving as a comprehensive guide. The practical examples demonstrate Pillow's potential in creating complex image manipulations, while also noting the convenience of alternative, simpler apps for casual users.