Hybrid mobile app development involves creating applications that can run on multiple platforms, such as iOS and Android, utilizing a single codebase. This approach combines elements of both native and web applications, allowing developers to write code once and deploy it across various platforms. Hybrid apps leverage web technologies like HTML, CSS, and JavaScript, often wrapped in a native container, providing a cost-effective solution with faster development cycles while retaining the ability to access device features and deliver a consistent user experience across platforms.