What Does Theme Mean?
In computing, a theme is a visual pattern or collection of patterns that determines the look and feel of a graphic interface. Themes are applied to just about any computer program that relies heavily on graphic elements, such as a browser, software program or operating system. Themes incorporate both practical and stylistic considerations.
Techopedia Explains Theme
Themes have been part of digital computing since the earliest graphic interfaces. The SAGE (Semi-Automatic Ground Environment) Project is said to have developed one of the original multi-panel window systems in their real-time graphic environments, which was important to the gradual development of the thematic visual interface.