The Ideal Burndown chart, in the preceding diagram, represents how work should be completed over time in a Sprint by the team. But in practical scenarios, the estimated values don't work in linear ways. There are days when more productivity is achieved and there are days when the curve may be stagnant.
Your team Burndown chart will also show the team state, as to whether the team is working at a sustainable pace or not. Use the Burndown chart throughout the Sprint to gauge progress and take corrective action when necessary, and also as a historic guide for planning the next Sprint commitments.
We will first discuss some typical Burndown charts which will give you some understanding about how a team is performing in a particular Sprint. The charts won't picture the actual nature and scenario for a team, but it is just an indication you can get from the chart.