An application that was developed for the computer it is running in. For example, a Windows app runs only in a Windows environment, and a Mac app runs only in a Mac environment.
Always the Fastest
Nothing is faster than a native client application because there are fewer layers of conversion between the executable code in the program and the operating system. In the desktop world, there are also non-native client options. For example, Java, JavaScript, Visual Basic and Silverlight programs all require runtime engines, which add a translation layer. In addition, native clients have access to the most low-level operating system and hardware features. See
interpreter.