Hi Naweed,
When you're viewing a report, there is usually a section below the chart labeled About this Report that you can expand for more info. When I did this for my Burndown chart, I saw the following info:
This report plots the remaining backlog of work in terms of the time estimated to complete it. Agile development methodologies such as Scrum use a burndown to plot the daily progress toward the end of a sprint.
Ideally, the chart will show a trend toward zero hours of remaining work as the sprint comes to a close.
Only work items which are open and in progress and which have an estimate specified are included in the calculation.
The blue line indicates the burndown, or remaining work in hours. The grey line indicates planned work, or the sum of the remaining work and the completed work. The "Ideal" line indicates what an ideal iteration would look like with a steady burndown from the beginning to the end of the iteration. The ideal line uses the last data point for planned work as its starting point. The "Expected Complete" line is a forward-looking plot from the current state of the burndown line to the end of the sprint, indicating the required rate of workj if the iteration is to complete successfully.
