Software development methodologies are structured approaches used to plan, execute, and manage software projects. They provide frameworks that help teams organize their work, ensuring that software is developed efficiently and meets user requirements. Common methodologies include Agile, Waterfall, and Scrum, each with its own processes and principles. These methodologies guide teams in collaboration, task management, and quality assurance. For instance, Agile emphasizes flexibility and iterative progress, while Waterfall follows a linear sequence of stages. Choosing the right methodology can significantly impact a project's success, influencing timelines, budgets, and overall product quality.