Definition - What does Task Pane mean?
A task pane is a dockable dialog window feature available in Microsoft Office, beginning with XP. This dialog enables the user to manipulate the data inside a document. An Office task pane opens at the right-hand side of the window that is being worked on and the task pane contains one or two pages with each page broken into sections for easy viewing.
Techopedia explains Task Pane
The task pane is a utility feature that helps the user have quick access to common features, information and commands in Microsoft Office 2002 (XP), Office 2003, and later versions. If using a compatible Microsoft Office version, the user can access the task pane by pressing CTRL + F1 from the keyboard or by clicking View and then Task Pane. The way the task pane appears on the screen can be modified to view, dock, undock, add pages and other such functionalities that MS Office allows.