Whether it's personal grocery lists, or large professional projects, every task can be broken down into smaller steps (subtasks) which are added and displayed in the task window:
Subtasks work the exact same way as normal tasks, so you can drill down into subtasks as far as you need to, and share them with appropriate parties. Those parties will not have access or view anything above their root subtask. Also, each subtask has its own notes.
Example Task: A (Added by Joe)Joe can see all of the subtasks, but only Jane, Bob, Larry, Suzy, Jen, and Kate can see their subtasks.