Agile software development is an iterative and incremental approach to software development. It emphasizes on flexibility, collaboration, and customer satisfaction. Agile methodology prioritizes individuals and interactions, working software, and customer collaboration over processes and tools.

Agile was developed in response to the limitations of traditional software development methodologies like the Waterfall model. In the Waterfall model, the development process is divided into sequential stages and each stage must be completed before the next one can begin. This rigid approach often leads to delays and inflexibility in responding to changing customer needs.

Agile methodologies, on the other hand, follow an iterative and incremental approach. The development process is divided into small, manageable iterations called sprints. Each sprint focuses on developing a working, tested piece of software that can be delivered to the customer for feedback. The development team collaborates closely with the customer throughout the process, making changes and adjustments as necessary.

Agile methodology also emphasizes on continuous improvement. The team regularly reflects on their work and identifies areas for improvement. This helps the team to adapt to changes quickly, respond to feedback effectively, and deliver high-quality software that meets customer needs.

Some popular agile methodologies include Scrum, Kanban, Extreme Programming (XP), and Lean Development. These methodologies provide a framework for implementing agile practices and principles. Agile has become increasingly popular in software development and has been adopted by many organizations globally.