Graphic design is the process of communicating ideas and information with color, images and typography. Applications of graphic design include, but are not limited to signage, electronic visual media, educational media, public information, advertisement, packaging, product design, and personal communication.
In short, if you can do it with words and pictures, an experienced designer can make it work better. Looking better is not always the goal, though it is nice. Sometimes you just need to find something, like an exit or a restroom or a safety warning.