Lists help you separate your tasks based on the context in which it makes sense to work on them. (i.e. Work or Personal)
Enable/Disable lists in Menu/Lists.
Here you can also add, delete and rename lists, and move tasks from one list to another.
Change the list you are working on by tapping the left button on the navigation bar and selecting the desired list.
The method of working on tasks stays exactly the same but it only applies to the tasks in the selected list.
Move the task from one list by tapping the list name (while editing the task)
Lists are available in premium versions after v1.9.