This to do stack is for keeping track of tasks during the day. The best use case is when you're working on Task 1, then you get distracted or take a break, come back and start work on Task 2, only to realise hours later you didn't finish Task 1
There are buttons for ordering the tasks, the most important thing is that your top 1, 2 and 3 are in the right order
The calendar and rollover feature lets you use it each day and grab remaining tasks from the previous day and continue with them today