See also: Tasks, Work Items-Ribbon, Edit Task dialog box
Open Task button enables you to open an existing Task.
Steps:
On the docked split container, in the Details
node, click Tasks.
Click the hyperlink (Subject field) to open the task. The task opens.
OR
Select the task that you want to open.
On the ribbon bar, in the Work Items/Tasks group, Open Task button. The task opens.