Since commonly multiple persons are working in one SharePoint-workspace, it is sometimes helpful to get notifications on activity in certain subpages. To get notifications too, you first have to create a new subscription-rule under the tab "PAGE" in the SharePoint menu bar. If you do not find such a tab in the menu bar, you should navigate to the root page of your SharePoint-department. In the subitem "Alert Me" click on "Manage My Alerts".

You are redirected to a new site, where you can add, delete and edit rules for notifications.

Choose "Add Alert" to add a new rule for notifications. Now you can select for which department you would like to receive notifications. You can only select one department per rule.

Your new rule appears in the list of notification rules. There you can delete it or - by clicking on the rule itself - edit it. The edit dialog is equal to the rule-creation dialog.