What are feature flags and how do you manage them?

Feature flags (toggles) control feature availability without deploying new code. Types: Release (gradual rollout), Experiment (A/B testing), Ops (circuit breakers), Permission (user-specific features). Benefits: decouple deployment from release, trunk-based development, quick rollback, progressive rollout. Management: use feature flag service (LaunchDarkly, Unleash), clean up old flags, document flags, test both states. Challenges: code complexity, testing combinations, stale flags. Essential for continuous deployment.