Inbox rules allow you to filter messages based on a certain criteria:
and to perform certain actions on them:
Once you log in, click on Settings in the upper right hand corner of the screen, then select View all Outlook settings.
In the Settings menu, select Mail and then select Rules.
Click "Add new rule". Choose the type of rule you wish to create, this will decide what you select for 'When the message arrives' and 'Do all of the following.'
Click OK to finish creating the rule.
You will then be able to view and edit the rule from the Inbox and Sweep Rules menu.