What does the Cumulative Flow graph tell me?

This graph presents the build-up of tasks on your board over time.
The horizontal line shows the time passed, while the vertical line indicates the number of tasks in different columns/workflow stages.
Each column is signaled by a different color.

Naturally, the bottom band, representing the rightmost column - which usually is for done work, will always be growing higher, for as long as completed work keeps building up.
That’s why the diagram usually takes shape of a rising slope.

What is more interesting, from an analytical point of view, are the top bands of the graph - those that represent the tasks in progress or waiting to be worked on.
Ideally, you should be looking for the team to achieve an evenly looking in progress band, as that would suggest work being completed at a constant pace.
As soon as you begin noticing that the in progress bar displays jumps, ditches, and general unevenness - that’s a sign, that work is not being completed, tasks get stuck and pile up in preceding columns as a result, with top bands getting wider.

The CFD is also a great tool for finding out when any extra help can be of use - if you notice that bands representing to do types of columns are getting wider, despite the doing bands progressing evenly - you may need to consider hiring extra team members to help with the workload.

Note, that you can switch particular bands of workflow stages on and off, by clicking their names at the bottom of the graph. Great for when you want to focus on particular workflow stages only:

You can also zoom in on a particular time frame by simply highlighting it with the mouse cursor.