The 'My Tasks' section at the bottom of your home screen displays all tasks that you own or are assigned. When you create a task for a contact, it will automatically route to 'Pending Tasks'.
Whenever a task is completed by the contact, the task will automatically route into the 'My Tasks' section to indicate that it needs your attention. You will also receive a notification.
To view all tasks, click 'Tasks' in the menu on the left side of the screen. Here, you can filter by a number of options such as the task type, who created the task, the due date, and so on.