The key principles of Agile include customer collaboration over contract negotiation, responding to change over following a plan, working software over comprehensive documentation, and agreement over processes and tools.

Benefits of Agile software development include faster delivery of features, improved product quality, better alignment with customer needs, enhanced flexibility and adaptability to changes, increased team collaboration, and continuous improvement through iterative feedback.

Agile differs from traditional software development in its iterative approach, where development is done in short, incremental cycles. Traditional methods, like Waterfall, follow a linear and sequential approach. Agile emphasizes flexibility, customer feedback, and collaborative teams, while traditional methods prioritize comprehensive upfront planning and documentation.

Common Agile methodologies include Scrum, which focuses on sprints and daily stand-up meetings; Kanban, which visualizes work in progress and limits work items in various stages; and Extreme Programming (XP), which emphasizes technical practices like test-driven development and pair programming.

Essential roles in an Agile team include the Product Owner, who defines the product backlog and prioritizes work; the Scrum Master, who facilitates the process and removes impediments; and Development Team Members, who are responsible for delivering the product increment.

Agile handles changing requirements through its iterative development process. Each iteration, or sprint, allows for reassessment and adaptation based on customer feedback and changing market conditions. This flexibility ensures the final product better meets user needs.

A sprint is a time-boxed iteration, typically lasting 1-4 weeks, during which a specific set of work is completed and made ready for review. Sprints aim to produce a potentially shippable product increment at the end of each cycle.