A skin is a file or package that changes the appearance of a program or operating system's interface. Skins provide a graphical user interface (GUI) overhaul for an application or operating system, allowing users to customize the look and feel of software on their device. Some applications use the term "theme" instead of skin, often to imply subtler changes rather than a full GUI transformation.
Since building in support for skinning takes extra development effort, relatively few applications support it. The use of skins that completely redesign an interface is generally limited to media players like WinAmp and VLC. Support for simpler, customizable themes is more common, including in web browsers like Google Chrome. Applications that support themes often include built-in theme galleries that let you browse and apply themes to change colors, fonts, and icons.
The Android operating system allows device manufacturers to include a skin that changes the appearance of the entire interface and introduces new functionality. However, these skins are not easily customizable by the device's owner. Changing an Android device's skin requires you to root the device or install separate software not included by the manufacturer.