The Trending - Survey Summary widget shows a percentage of each answer option over time.
The number of periods displayed on the widget starts with the latest month set through the global settings and goes 'backwards' through months for the number you specified. For an example, if you set the number of periods to 3 (and keep the starting month as January), the data displayed would be for January, December and November of the previous year.
The "Columns" widget settings allows you to display the data in five different ways. The settings are similar to those of the Survey Summary widget.
Points lost displays the amount of points lost in the time period, for the selected questions.
Breakdown setting displays either Averages or Sums details for the selected questions in the time period.
Potential Impact is the amount that the overall score would have increased if the question was answered perfectly.
Potential Evaluation Score is the overall score that the evaluation would have if the question was answered perfectly.
And Question Score (displayed in the first screenshot), as the percentage of possible score achieved for this question.
Remember to check a different help article detailing most of other settings of this widget.