A Manual Task is a task that is performed without the help of any business process execution engine or application. It models work that is done by an external person which the engine doesn't need to know. The engine handles the manual task as a pass-through activity where the process is continued automatically when the process execution arrives into it.
Eg: A delivery boy delivering pizza
1) The user enter the details of the pizza he/she wants to order which includes the topping and the size.
2) Next the user has to confirm the order by entering the amout.
3) Then the pizza delivery boy will deliver the pizza to the user: Manual Task
4) The user then confirms the status of the delivery.