In computing, a theme is a preset package containing graphical appearance and functionality details. A theme usually comprises a set of shapes and colors for the graphical control elements, the window decoration and the window. Themes are used to customize the look and feel of a piece of computer software or of an operating system.
Also known as a skin (or visual style in Windows XP)[1] it is a custom graphical appearance preset package achieved by the use of a graphical user interface (GUI) that can be applied to specific computer software, operating system, and websites to suit the purpose, topic, or tastes of different users. As such, a skin can completely change the look and feel and navigation interface of a piece of application software or operating system.
Software that is capable of having a skin applied is referred to as being skinnable, and the process of writing or applying such a skin is known as skinning. Applying a skin changes a piece of software's look and feel—some skins merely make the program more aesthetically pleasing, but others can rearrange elements of the interface, potentially making the program easier to use.