Feature flags, also known as feature toggles or switches, are integral to modern software development, allowing developers to control the visibility and accessibility of features within applications. These tools are vital for managing feature releases in continuous deployment (CD) environments, where agility and automation are crucial. Feature flags help mitigate risks and enhance user satisfaction by decoupling feature releases from code deployments, enabling rapid and controlled rollouts, A/B testing, and swift rollbacks when necessary. Various types of feature flags, such as release, operational, experimental, and access control flags, offer developers flexibility and control over feature management, ensuring stable and reliable software delivery. However, their implementation requires careful planning to avoid challenges like flag proliferation and testing complexity. By incorporating feature flags into CD practices, development teams can deliver bug-free, stable software more quickly and efficiently, leveraging platforms like CircleCI to enhance their deployment pipelines.