Often the words "attribution" and "citation" are used interchangeably, however with digital images the words can have slightly different meanings depending on your use of an image.
The act of establishing a particular person as the creator of a work of art.
Attribution has to do with acknowledging the person/s who hold the copyright license of an image. You would attribute an image used in presentations, papers or other formats that do not require a specific citation style. For example, if you use a digital image - maybe a photograph you found on Flickr - to enhance a web page, or a PowerPoint presentation you need to attribute the photograph to the photographer.
Attribution is about crediting a copyright holder according to the terms of a copyright license, usually crediting artistic works like music, fiction, video, and photography.
The act of acknowledging the work of another within a scholarly context.
If you are writing an academic paper and use an image to support an idea or argument then you would cite that image according to a particular citation style eg., MLA or APA. This involves providing all the information about the image as well as attributing the copyright holder.
Citation is a scholarly practice for tracking the ideological underpinnings of a work, usually referencing sources like published books, articles, government documents, primary sources, etc.
Real-Live Attribution in Action
Any image you plan to use in a scholarly work should be cited and/or attributed to the copyright holder of the work. This includes: