OfficeTalk lets you link items of many different types together, allowing you to easily associate one piece of information with another. For example, you may need to action a task as a result of a conversation that you had with a particular contact. OfficeTalk will let you link together the task, the conversation and the contact so that you can quickly access each piece of information from the other.
OfficeTalk lets you link information belonging to other users, provided that you have access to their information. For example, you may send a mail message to somebody requesting that they action a task that you have entered for them in their task list. You may wish to link your copy of the mail message to their task, letting you find the task quickly to see if it has been completed.
More:
How to link two items together