Constants are global, literal values that will not change and that can be used in all definitions. They're created in _Settings, using the Constants element.
Constants are created, as shown above, as a parameter list and are accessed using @Constant tokens. For example, the value of the first constant in the list shown above would be available using @Constant.EditMode~. For more information on @Constant tokens, see Token Types.
The use of constants provides a way to have values referenced throughout your application while only defining them in a single place, which makes maintenance very easy. Constants are often used for values that might change between development and production environments.