The Peaks tab shows a summary of your activity's peak power, heart rate, or pace. For activities with multiple metrics, you may toggle between metrics on the peaks graph. In addition to showing the peaks from the activity, the Peaks tab will also display your best achievements from past activities. Select the desired time period from the drop down on the upper right of the graph to adjust the other values shown on the graph. In addition to graph, the values are also displayed in a table format below the graph. 

Details for each time duration can be viewed by hovering over the point on the graph. For each value in the peak power table, you can click the value to jump to the point in the activity where this value was achieved. Additional options for the peak power table can be viewed by clicking the menu icon in the upper right corner of the table.