if feature_enabled("new neat thing") { doNewNeatThing() } In principle that's it. How exactly it decides true vs false can be as complex as needed -

if feature_enabled("new neat thing") { doNewNeatThing() } In principle that's it. How exactly it decides true vs false can be as complex as needed - hardcoded, config files, fully dynamic, etc. It's defined more by the use than by what it is / how it works. E.g. a number of teams I've seen use them to dogfood their team's features (e.g. via user ID) for a brief period as a final check before wider release (which is also rolled out by that feature flag in %-batches or other criteria). It also gives you an easy dynamic "off" switch if something isn't working out or is causing errors. Server-side that may or may not be particularly useful, but in apps with week-long review delays it can be the difference between "a brief burst of issues for a few people" and "our app is totally broken for a week, customers are ANGRY".