A task is a piece of work with an owner and a deadline
A task tells a specific person, or everyone in a role, that something needs doing at a site by a certain date. Deliver mounting rails to Himalaya Higher Secondary School by 18 September, for example, is a task for the field staff member who covers that school.
Every task belongs to one project and one site, has a Status, a Priority and a Due Date, and keeps its own history of who did what. Some tasks are created by hand; many are created for you — when a form is scheduled, when a case needs review, or when a workflow decides a follow-up is needed.
Tasks appear in three places on the web: the project's TASKS tab (every task in the project), a site's TASKS tab (that site only) and My Dashboard → TASKS (tasks assigned to you). On the mobile app, field staff see their tasks in the Tasks tab.