Create a task by starting a paragraph with a hyphen then a space. The hyphen will change to a task and then you are free to style the paragraph was you wish. You can edit the priority %complete and due dates in any of the following three ways
By swiping to the left to reveal the Task Pane and tapping on your task from the list
By enabling the Task Helper switch in settings and then tapping on the coloured priority icon next to the task in the right hand margin.
If you have a keyboard and the cursor is anywhere within the task paragraph selecting the keyboard combination of ⌘ ctrl T
Each of these actions will bring up the task popup where you can set % Complete - Priority(1,2,3 or Zzz) and a due date(deadline) tapping the X in the popup or anywhere outside it will cause the popup to disappear and you changes to be saved
To mark a task complete you can tap the incomplete task symbol [ ] and it will change to ☑ indicating the task is complete or in the task editor popup you can slide the % Complete to 100% and it will auto mark it off for you
Task Groups
Task Groups or Projects are a special paragraph that is started with the + symbol then a space
Task Groups display a completion status of all associated child tasks at the same or greater indent level via a graphical circle indicator
You can even nest task groups in an outline structure and the top level group will only show complete if all the associated child groups are complete
Task Groups help you break down complicated tasks into smaller sub-tasks to ensure you stay on track to meet your goals