Roadmap milestones are the key waypoints or checkpoints on a product roadmap that indicate progress towards a larger goal or objective. They help product managers and teams stay on track and measure their progress. Imagine you're planning a road trip - your roadmap is the route you'll be taking, and the milestones are the important stops along the way. These could be specific features, product launches, or major updates that need to be achieved to reach the ultimate destination. Roadmap milestones keep everyone aligned and provide a sense of accomplishment as you move closer to your product vision.