Feature flags allow developers to gradually rollout new features to specific users or groups, expand or rollback changes without redeploying code, and test features with real users. They separate code deployment from releasing business logic, enabling developers to get feedback and analytics before full release. Feature flags also eliminate long running branches and merge conflicts that occur in traditional release processes. The document recommends best practices for feature flagging like defining the right level of flagging, avoiding ambiguous or misunderstood flags, controlling access, adding visibility for non-technical users, and logging dependencies.