This is used to display the sequence of pitches in a baseball At-Bat, along with the outcome of the At-Bat. The inner-most ring shows the outcome of the At-BAt (strikeout, single, groundout, etc.). Green arc's represent a positive outcome (when the batter is out), and red arc's represent a negative outcome (when the batter reached base). Moving outwards, the next ring shows the first pitch of the At-Bat, and then the second pitch, third pitch, etc. The different shades of blue represent the different types of pitches the pitcher is throwing.
Hover over an area of the visualization to show what percentage of At-Bat's follow that pitch sequence. Hovering will also show the order of the pitches, and the result of each pitch (ball, strike, foul, in play) in the upper left hand corner. The count (balls and strikes) is also displayed directly under this text sequence.