A heatmap is a visual representation of user behavior on a webpage, using color gradients to show where visitors click most (click maps), how far they scroll (scroll maps), and where their cursor moves (move maps). Tools like Hotjar and Microsoft Clarity generate heatmaps to reveal how real users interact with page layouts. Heatmap data is invaluable for CRO, helping identify friction points, underperforming CTAs, and content that users ignore.