In the default mode, tasks are grouped according to their status 1: Open, In Progress, Done or Closed.
It is also possible to group them by priority 2: Highest, High, Medium, Low, Lowest, and by people 3, including virtual resources. In the latter case, all the unassigned tasks will be displayed in a separate column.
Another worthwhile possibility that allows for additional customization of your board is grouping tasks by some Custom fields you have created in your project.
Check here how to create a custom field and group your tasks in a way that is most convenient for you.
Grouping is possible for the following types of Custom fields:
Find out more about types of Custom fields available in GanttPRO here.