In the experimentation ecosystem, experiment surfaces are described as features. A feature is an area of code instrumented with telemetry and accessible for remote configuration. It can be as small as a single function or as complex as a whole page. Some examples:
aboutwelcome: The about:welcome page in Desktophomescreen: The homescreen page in FenixtabTrayFeature: The tab tray in Firefox iOS
Features are defined in a Feature Manifest file for the application, and the client code uses the Nimbus SDK to access variables associated with those features.
#To define your feature in the feature manifest file
First, look at what is already defined in the manifest file: