The key principles of Agile software development include iterative progress, collaboration, and flexible responses to change. Agile methodologies prioritize customer feedback and adaptive planning, allowing teams to develop and deliver functional segments of software frequently. Key frameworks, like Scrum and Kanban, emphasize teamwork and visual management, driving effective communication. This approach enhances project visibility, ensures quick adjustments based on stakeholder input, and promotes a culture of continual improvement, leading to successful project outcomes.