Definition - What does Burndown Chart mean?
The chart provides project team members, managers and business owners with a common and easily understandable view of work progress.
Techopedia explains Burndown Chart
Burndown charts can have one or many elements, depending on the level of required detail. A very basic chart shows only the completed work against the time remaining until the end of a project, while more detailed charts have elements like velocity, actual work done and some labels indicating who is doing which task.
The velocity is the ideal line that represents how the work should progress. Usually, it is just represented as an even, straight line starting from the maximum amount of work to zero work on the deadline and shows a uniform distribution of work done. But if it needs to be more specific and highlight work complexities, then the project manager can make an ideal velocity that is not straight. Nine out of 10 times, velocity is not achieved, and the actual work done is usually shown to be above the velocity line, signifying less work finished. However, sometimes it may be below the velocity line, which indicates that the team is ahead of schedule, and there is slack time.