The heatmap provides a visual representation of how accurately you type. Each “blob” on the heatmap represents a key on the keyboard. When you begin using SwiftKey, each blob is a perfect circle, representing average accuracy. As you use SwiftKey these blobs are morphed to fit the region that you tend to press when you want to use that key, thereby representing the unique way in which you use the SwiftKey Keyboard.
This visualization also lets you see your own accuracy and shows the area SwiftKey associates most strongly with each letter. As you type, this is combined with other statistical data to provide the best estimate of what you intended to say.