The Agile development methodology has its roots in 2001, where it was first described at a small conference. It emphasizes flexibility, adaptability, and collaboration between teams and individuals. The Agile manifesto values individual interactions over processes and tools, working software over comprehensive documentation, customer collaboration over contract negotiation, and responding to change over following a plan. There are different agile methodologies such as DSDM, Scrum, and XP that can be implemented to achieve agility. A feature team is a cross-functional team that completes many end-to-end customer features in a short iteration cycle, allowing for continuous delivery and adaptation to changing requirements. Short iterations, test automation, and regression testing are fundamental tools for agile development, which enable software to work quickly and continuously integrate changes. Agile development is particularly suitable for mobile app development due to its need for frequent releases, bug removal, and feature addition to keep users engaged.