Using Gantt with Lists

If you are managing tasks through a workflow in Column View, something like Backlog > In Progress > Blocked > Done, seeing those lists in Gantt may not be that useful. (BTW, for this you would have Show Lists turned off which is the default setting)

However, if you are using List View or managing a waterfall project, something like:

Discovery
Design
Development
QA

Seeing lists in your Gantt may not only be useful, but necessary. 

To view lists in Gantt, click the Settings > Show Lists

You will now see your lists in the left task pane.