You can change the userID in a ToDo list to be able to perform work for someone else. This is called WOBO or Working on Behalf Of Someone Else. This lets you continue the work of a fellow employee who is on vacation, sick, or for some reason is not connected to the system. by moving through their activities for them. The group work flow goes on, and everyone's activities are processed on time. Every activity changed or completed in someway will carry the new target (userID) of the person who changed or completed the activity. Each activity selected in WOBO will have the word WOBO displayed at the top bar on the righthand side of the contact record.
You switch to WOBO by using the ToDo List but you can also use Authored Activities, Completed Activities, and Message Activities lists as well. When the ToDo list appears, enter the user ID for the person you want to work on behalf of and press enter. This puts you into WOBO status, where you remain working until you switch back to your own status, or switch to work on behalf of someone else.