You may have the right to create, view and submit expense reports on behalf of a colleague.
Your colleague must first delegate this right to you - see Delegating Submission of Expense Reports.
If you have this right, you see an additional section on your Home tab showing your colleagues' reports:
In addition, your Expense Reports tab enables you to see both your own reports and those of your colleagues for whom you have this right:
The drop-down list enables you to choose which reports to display. You can choose to see:
all reports to which you have access
all your colleagues' reports to which you have access
just your reports