The function of a product backlog in agile development is to serve as a prioritized list of project requirements and tasks that the development team needs to complete. It acts as a dynamic inventory of features, enhancements, and bug fixes that are essential for the product's evolution. The product backlog is continuously refined through collaboration between stakeholders and the team, adjusting priorities based on feedback and changing business needs. This agile approach ensures that development efforts remain aligned with customer expectations, allowing for quicker responsiveness and iterative improvements over time.