Adobe Photoshop is a graphics editing program developed and published by Adobe Systems Incorporated. wikipedia.org

Digital art is an artistic work or practice that uses digital technology as an essential part of the creative or presentation process. wikipedia.org

A sketch is a rapidly executed freehand drawing that is not usually intended as a finished work. A sketch may serve a number of purposes: it can be used to record something that the artist sees, develop an idea for later use or as a quick way of graphically demonstrating an image, idea or principal. wikipedia.org

Computer illustration or digital illustration is the use of digital tools to produce images under the direct manipulation of the artist, usually through a pointing device such as a tablet or a mouse. wikipedia.org

Drawing is a form of visual art that makes use of any number of drawing instruments to mark a two-dimensional medium. Instruments used include graphite pencils, pen and ink, inked brushes, wax color pencils, crayons, charcoal, chalk, pastels, various kinds of erasers, markers, styluses, and various metals. wikipedia.org