Tasks
A task is a note with an owner. Assign a note to a team member, give it a due date, and settle it when the work is done.
A note with an assignee
Every note can have an assignee, and a note that has one is a task, so a task can concern anything a note can. Mentioning someone asks them to look, and assigning the note makes them its owner. The composer offers both together.
Who can be assigned
The assignee must be a team member with access to the project. Anyone else is refused, with a message that names the id and says it has no access to this project. Assignment also grants read access: a private note opens to its assignee, and unassigning closes it again unless they are also mentioned.
Your users never see assignment. A signed-in user who sent a note sees whether it was settled, without the assignee or the progress counts.
Sub-tasks, progress and due dates
Sub-tasks use the same parent link as replies: a child note with an assignee is a sub-task, and one without is a reply. Every note reports how many direct children it has and how many are settled (1 of 3 done, for example), counting only the children the viewer can see.
A note has its own dueDate, separate from any mention's. Ordered by due date, a list becomes a queue with the soonest first and undated notes last. Filter by assignee for one person's queue, across the project or on a single subject. From the command line, foir notes assign sets the owner.
Settling
A task is done when its note is settled, which the API calls resolved. In the console that takes one click, a reason can be added afterwards, and reopening clears the reason. Settling never cascades: a settled parent leaves its children as they were. It is independent of assignment too, so settling does not unassign and reassigning does not reopen.
Read the detail
The tasks section of the notes guide covers assignment, sub-tasks, progress, due dates and filtering by assignee.