By default, Tezzera sorts your tasks by their due date both in List and Board View.
But in List View, you do have the ability to re-order your tasks differently.
Your first option is to manually drag and drop your tasks into a different order. This will override the date-based sorting.
Your second option is to use the sorting feature to instantly re-order your tasks. To do this, simply click on the heading of the column that you'd like to sort by. Clicking the heading once will sort your tasks by that variable in ascending order. Clicking it twice will sort in descending order. And clicking it a third time will reset or clear the sorting feature so that your tasks go back to the way there were before.